It was prior to 1987 when Gene Roddenberry opened The Next Generation for story ideas from writers, though most of the earliest TNG plot concepts were rejected by him. (Star Trek: Communicator issue 114, p. 56) Producer Robert Lewin later remembered, "There were a great many writers pitching to write the show. Several had story ideas with potential. He was shooting almost everything down because it didn't fit his concept of what the 24th century should be [....] The first scripts were not terribly good. I think only one was shot." (Cinefantastique, Vol. 25/26, No. 6/1, p. 85) David Gerrold recalled, "I'm meeting with writers, taking pitches, I'm told pitches are good to go to outlines; later Gene calls me into his office and says, 'We’re not buying those stories.' 'Why?' 'Their credits are junk.' 'Gene, what are you talking about? Their credits are not junk. These are proven writers.' [....] I was still getting calls from agents. I told them, 'I think we’ve got an edict from the studios that we’re not to talk to new writers right now.' I got called into Gene’s office again. 'Don’t you dare tell agents that! There’s been no edict. It’s my decision.' The first time he tells me that the studio says we can’t buy those scripts because the writers have junk credits. In that first meeting I said to him, 'What should I tell the agents?' He said, 'Lay it off on the studio.' So I lay it off on the studio, he calls me back into his office and says, 'How dare you lay it off on the studio? It makes me look like I’m not in control of my own show.' 'Gene, that’s what you told me.' 'I said no such thing.' 'All right, Gene, you’re the boss. Do you want my resignation?' 'No, I don’t want your resignation, you’re doing fine work,' and he started backing down." (The Fifty-Year Mission: The Next 25 Years, pp. 70-71, 72-73)
Many of the first abandoned plot ideas featured Klingons. Richard Arnold explained, "Gene kept getting stories from professional writers about wars with the Klingons and he kept saying, 'Star Trek is not about Klingons!'" (Star Trek: Communicator issue 114, p. 56) Many, many other undeveloped episodes involved the character of Jack Crusher. 
Roddenberry frequently scrapped stories even he himself wrote. Maurice Hurley remembered, "He would come up with a story, say this is the story we want to do, then when that story was written out, he'd want to tear it up and throw it away. 'Oh, no, no. I got a better idea.'" (William Shatner Presents: Chaos on the Bridge)
For TNG's first season, Fred Bronson pitched multiple ultimately never-made episodes to Robert Lewin. "I had about half a dozen stories," he noted. Bronson learned Susan Sackett had similarly been pitching ideas to Gene Roddenberry without much success, so the two decided to team up at the start of the second season. After Michael Piller arrived to take on the writing staff in the third season, numerous other undeveloped tales were offered to the series by Bronson and Sackett. "We got our appointment with Michael Piller and went in to pitch, and we had about a dozen ideas," Bronson recalled. "We went through every one of them, and it was 'No, no, no....'" Hence, most of these narratives were denied an opportunity to be produced, although the last one they suggested was subsequently bought and turned into the Season 3 episode "Ménage à Troi". (Starburst, Special #29, p. 56)
At one point in the second season, Maurice Hurley became so frustrated with the egos of the main cast that he proposed to Rick Berman a story arc that, if made, would have brought about some of the most radical changes in the format of the entire series, to allow for all the principal actors to be fired. Hurley recalled the premise: "I'll build the second season on the absolute tragedy that the Enterprise exploded by unknown cause and lost everybody, and now we must find the new Enterprise crew." (William Shatner Presents: Chaos on the Bridge)
Robert L. McCullough was another writer who pitched some never-developed story ideas for the series. "I must have pitched 20 episodes," he reckoned. McCullough also implied that he pitched these concepts to Gene Roddenberry. (Starlog, issue 187, p. 55)
From early 1990, years prior to working on Star Trek: Voyager and Star Trek: Enterprise, Mike Sussman sent three spec scripts to the TNG offices, while residing in Florida. They were all rejected, which Sussman laughed about decades later. Nowadays, he no longer has any of the three scripts and regards them as "terrible." 
In his book Trek: The Unauthorized Behind-The-Scenes Story of The Next Generation, James Van Hise explored several never-filmed episodes written for Star Trek: The Next Generation, most notably a controversial episode written by David Gerrold, entitled "Blood and Fire".
Prior to serving as science consultant on TNG for its seventh season, André Bormanis submitted numerous story pitches to the series. They impressed the TNG staff despite neither of the ideas being produced for TNG. (Star Trek Monthly issue 25, p. 38)
Some stories had to be abandoned because the writing staff couldn't figure out how to make them work. Ronald D. Moore archived the stories that were never produced, whose quantity wowed Brannon Braga. "I have binders of all the abandoned stories," Moore revealed, "and all the ones we bought, the ones we started to develop. But they filled, like, a three-ring binder; each season was filled with stories that we didn't get to. Some were pitches, some were internally developed, some never made it past just the one-page memo. But there are dozens, if not hundreds, of stories that we didn't do." (All Good Things (Blu-ray) audio commentary)
Ronald D. Moore wanted Worf and Deanna Troi to, at one point in the series run, be married to each other. Though that ultimately didn't happen, Moore revisited the notion while writing DS9: "You Are Cordially Invited", in which Worf weds Jadzia Dax. (Star Trek: Deep Space Nine Companion, p. 503) Troi ended up marrying William T. Riker in the film Star Trek Nemesis.
Another character concept that was repeatedly considered for TNG but never used in the series was a mischievous son of Guinan. The notion provided the basis for the character of Martus Mazur, in DS9: "Rivals", though the idea he was Guinan's son didn't make it into the episode's final version. (Star Trek: Deep Space Nine Companion, p. 109)
An episode apparently involving the theme of abortion was planned but shelved. (The Fifty-Year Mission: The Next 25 Years, p. 277) Abortion was alluded to in "The Child", with Worf arguing that Troi's anomalous pregnancy should be terminated for the safety of the ship, and Troi asserting that she had the right to choose to continue the pregnancy.
"All Good Things"
Ronald D. Moore and Brannon Braga conceived of a two-parter for season six titled "All Good Things". In the story, Starfleet recalled the Enterprise back to Earth and was planning to split the crew up, reassigning the officers to various different posts. The Enterprise would become, in Moore's words, "the Queen Mary, basically," and the crew, on the way home, would all decide what they were going to do with their lives. However, on the course of returning home, a battle with an alien ship took place, the saucer section separated from the battle section, which exploded, and the saucer crashed on an alien planet. Braga claimed there was a desire among the writing staff to destroy the Enterprise-D and give the crew a new ship, and the show a new style, in its last season. The story was rejected because, in Moore's words, the producers hated the idea. It was rejected most likely because of the plans for The Next Generation to transition to film, the following year, where the Enterprise-D and other familiar elements were desired. This pitch, however, ended up influencing the series finale "All Good Things...", which got its name from this pitch, and Star Trek Generations, where Moore and Braga were able to realize their desire of having the Enterprise-D be destroyed, in an identical crash scene envisioned for the episode.. (The Fifty-Year Mission: The Next 25 Years, p. 326)
"All That Glitters"
One suggested plot which subsequently became legend around the Hart Building on the Paramount lot, where the series' staff writers worked, involved an encounter with Amish people. "One of the writers once took a pitch idea from an invited writer where – I swear to God! – Troi gets zapped to a planet of Amish people, and her whole purpose in life is to milk cows!" recalled Lolita Fatjo, with a wry smile. (Star Trek Monthly issue 5, p. 11)
Arthur Sellers script
Writer Arthur Sellers submitted an ultimately unused script. Remembered David Gerrold, "Arthur Sellers shows us a first draft script, and it's too heavy on the techno-jargon, but structurally correct. Arthur was so eager to please Gene [Roddenberry] that he went to talk to Rick [Sternbach] and Andy [Probert] about the science. He wanted the science to be accurate. Rick and Andy got enthusiastic and invented some great stuff for him. Gene reads the script and hits the ceiling. 'This is bullshit science. Not on my show.' The funny thing is that these things were really science. Gene said, 'If I call my good friend Isaac Asimov and ask him, would he understand?' Arthur said, 'Probably, since we got this out of scientific articles.' He calls it bullshit and then throws it out [....] So Arthur Sellers' script got cut off." (The Fifty-Year Mission: The Next 25 Years, p. 80)
A story pitched by Nick Sagan was to have featured a return of the character Armus, from TNG: "Skin of Evil". (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 293)
During the development of Star Trek: Voyager, the creative team of Executive Producers Rick Berman, Michael Piller, and Jeri Taylor considered writing an installment of TNG's seventh season which would have featured the character of Reginald Barclay completing the creation of The Doctor. The episode was intended to establish the invention of that holographic character before it debuted in the forthcoming series. Taylor referred to the concept in one of many compilations of development notes regarding regular meetings she was having with Piller and Berman. This particular series of notes was dated 6 August 1993 and stated, "Barclay would have been working on this program and finally takes a leave to put on the polishing touches (on a TNG episode). He creates the character in his own image." (A Vision of the Future - Star Trek: Voyager, pp. 182 & 183) As Stephen Edward Poe commented in his book A Vision of the Future - Star Trek: Voyager (p. 183), "Such an episode would, of course, have all the normal derring-do viewers had come to expect from a Star Trek episode. But that would be secondary. The real aim would be to establish the precedent for the Doctor [....] In the end, the producers abandoned the idea of writing this episode, probably because of the later effort required to establish the Maquis."
Big Bang alien
Ronald D. Moore pitched a story about an alien that lived in the fabric of space and had been "born" around the same time as the Big Bang. It would have revealed that, in the early time of the universe, these lifeforms were numerous, but because they lived within the fabric of space itself, as the universe expanded, they had become separated, with no means to communicate. This particular alien, as such, had been alone for literally billions of years, and so reached out to the Enterprise to alleviate its loneliness. It originally tried to communicate with the crew via intense hallucinations taken from their mind, in an effort to keep the Enterprise in its region of space. Eventually, Troi found a way to communicate with the alien, and the Enterprise crew agreed to inform Starfleet to leave a science station nearby to study the alien and communicate with it. 
"Blood and Fire"
"Blood and Fire" was a controversial episode written by David Gerrold. The episode's first draft script was dated 13 May 1987. It involved gay characters and an allegory to AIDS. The rejection of this episode partly led to Gerrold leaving TNG.
In a 2011 interview, Gerrold concurred, "My cause at the time was blood donorship, and I knew that people were so terrified of AIDS they had even stopped donating blood. So I wanted 'Blood and Fire' to be about the fear of AIDS – not the disease but the fear – and one of the plot points involved having the crew donate blood to save the lives of the away team. I thought, 'If we do this episode right, where blood donorship is part of solving the problem, we can put a card at the end telling viewers that they could donate blood to save lives, too.' I thought it was something Trek should be doing, raising social awareness on an issue, and if we did it right, we could probably generate a million new blood donors at a time when there was a critical shortage."
"There were two characters who were not very important to the story, but they were the kind of background characters you need. At one point Riker says to one of them, 'How long have you two been together?' That was it. The guy replies, 'Since the Academy.' That's it. That's all you need to know about their relationship. If you were a kid, you'd think they were just good buddies. If you were an adult, you'd get it. But I turned in the script and that's when the excrement hit the rotating blades of the electric air circulation device. There was a flurry of memos, pro and con. One memo said, 'We're going to be on at four in the afternoon in some places and we're going to get angry letters from mommies.' My response was, 'If we get people writing letters, it shows they're involved in the show, and that's exactly what we want. We want them engaged, and a little controversy will be great for us.' And I said, 'Gene [Roddenberry] made a promise to the fans. If not here, where? If not now, when?' But the episode got shelved anyway and that's when I knew I wasn't going to be allowed to write the very best stories we should be writing. The original show was about taking chances. If we weren't going to take chances, we weren't doing Star Trek. So I let my contract expire and I went off to do [...] other things." 
The story was included in the reference book Lost Voyages of Trek and The Next Generation (pp. 85-90). Gerrold later adapted and directed the script for the fan series Star Trek: Phase II. The episode also featured Denise Crosby.
"Blood and Ice"
"Blood and Ice" was Herb Wright's second draft of David Gerrold's "Blood and Fire". Wright kept the same basic adventure, but removed the allegedly gay characters and the AIDS allegory, replacing them with zombie crewmen. Having noticed that Star Trek: The Original Series features various types of stories, Wright – who worked on the first and fifth seasons of Star Trek: The Next Generation – suspected Star Trek allowed "room in the mix for Night of the Living Dead, zombies in space," in his words. He went on to say, "When I came back during fifth season, I read the script again because they were hardup for stories and I brought it in. I mentioned it to [Co-Executive Producer] Michael Piller and he said, 'What was it?' because he thought he had read everything when he came in. I said, 'You probably never saw this draft. If anything, you probably read 'Blood and Fire', and this one was called 'Blood and Ice'. I printed it out and brought it in. The staff loved it, Rick loved it, but Piller said, 'Nice script, but it's really a first season type of show.' Oh well." Thus, despite the rewrite, this version remained unfilmed as well. (Lost Voyages of Trek and The Next Generation, p. 93) The story was included in the reference book Lost Voyages of Trek and The Next Generation (pp. 91-93).
"The Bonding" was written by Lee Maddux. Apart from having the same name as the produced TNG episode "The Bonding", it was completely unrelated to that installment. The story was included in the reference book Lost Voyages of Trek and The Next Generation (pp. 67-69). A draft of the episode was dated 9 October 1987. (citation needed • edit)
Borg story arc
Maurice Hurley initially intended the second season to feature a two-episode story arc that would introduce the Borg into the series, forming a trilogy with the produced penultimate episode of the first season, "The Neutral Zone". As well as introducing the Borg, the two episodes were also meant to portray the formation of an alliance between the Federation and the Romulan Empire to counter the new threat. (Star Trek: The Next Generation Companion) However, due to a writers' strike in 1988, Hurley's plans for the arc had to be dropped. The introduction of the Borg was postponed until the second season installment "Q Who".
Jeri Taylor pitched two of her own ideas for a season six two-parter, both of which resembled the aborted "All Good Things" pitch from Braga and Moore, and both of which featured the Breen, a then-unseen race. In the first pitch, the Enterprise-D is recalled from deep space exploration to permanently guard the Sol System and capital of the Federation. Starfleet believes the Enterprise-D is too valuable to lose and other ships can do the same tasks. The crew reacts differently to this, and don't know what they're going to do with their lives. Picard is especially torn, as he is pressured to remain captain of the Enterprise. All the while, the mysterious Breen finally make contact with the Federation. Their flagship arrives on Earth to begin negotiations with the Federation, and it is decided that a joint scientific mission be conducted to smooth relations. The Enterprise-D and the Breen flagship are assigned the task, but the mission goes awry due to a spatial anomaly that reacts to warp drive. The Enterprise-D ends up crashing into a planet before the episode ends in a similar fashion to Star Trek Generations. 
Another similar idea Jeri Taylor had was William T. Riker being given command of the Federation starship Indiana, with some of its senior officer positions filled, at his request, by senior officers from the Enterprise. The Indiana began journeying to the Bajoran wormhole but, en route, the ship was hailed by a Breen delegation and was consequently reassigned by Starfleet to establish diplomatic relations with the Breen. After a Breen science vessel became trapped in an anomaly, the Indiana was about to attempt a rescue of the trapped craft and Jean-Luc Picard came to visit the Federation starship. Suddenly, however – as the story drew to an end – the Indiana itself began to be violently pulled into the anomaly, causing a rupture in a transporter room aboard the ship, and Picard, who had been heading back to the Enterprise, was blown out of the rupture. 
"The Changing Seasons"
"The Changing Seasons" was another ultimately undeveloped story. It involved time travel, the relationship between a father and son, as well as the death of William T. Riker. In a memo David Livingston sent Rick Berman (on 23 April 1990), Livingston gave a review of "The Changing Seasons", commenting, "I didn't buy this one for an instant." Livingston rejected the story for several reasons. These were: he highly doubted projections, implied in the story, that time travel would be "simple in a few years"; he was skeptical that the TNG production staff would want to deal with Riker's death, being of the opinion that the notion of someone dealing with their own mortality had been done better in "Yesterday's Enterprise"; he preferred that, if they depicted a father/son bond on the show, they do so with an idea he had submitted about Picard having a renegade son. 
Chaos theory story
An idea repeatedly pitched to TNG was creating a story that featured chaos theory. Joe Menosky remembered, "Writers would come in and say 'What about chaos theory?' And someone else would say, 'Well, what about it?' Everyone would struggle but nobody would devise a story." It was not until the writing of DS9: "Rivals" that such a story was conceived, forming the genesis for that episode. (Star Trek: Deep Space Nine Companion, p. 109)
"Charlie X" story
A sequel to TOS: "Charlie X", featuring the character Charles Evans, was pitched by Nick Sagan. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 293)
One such plot concept was thought up by Walter Koenig himself. "I was contacted by one of the writers to talk about what kind of story they could do with Chekov. We had lunch together, and couldn't come up with anything. So he asked me to come in and meet with all the writers; this was after Jimmy [Doohan] and DeForest [Kelley] had already been on and had both had very successful experiences," Koenig recalled in 2016.  In a 1998 interview, he clarified, "We talked about it when The Next Generation was on the air, and I had a meeting with the writing staff. At that point they were pretty determined that they didn't want to do a story that involved progeny of the original cast, or Time travel. So they were trying to come up with a story that would circumvent those prohibited ideas." (TV Zone, issue 107, p. 37)
Koenig went on to say that he did devise a story that would allow him to reprise his role as Chekov, but only after TNG concluded its series run, unfortunately. "I had [Chekov] as a mental aberration – I wasn't really there," he noted. "I was being hallucinated." Reportedly, the tale was centered around Worf, so it would have been fairly easy to make the story work for Star Trek: Deep Space Nine, after Worf joined the main characters of that series, though that never happened. (TV Zone, issue 107, p. 37)
In his 2016 interview, however, Koenig claimed to have had a plot idea at the story meeting, commenting, "In the interim, I had come up with an idea [for Chekov], and was very much looking forward to sitting down with them. We were in a room, and they had pads and pens ready to take notes. But just when we finished the introductions, the phone rang and it was [a producer] telling them they had to leave, that they were needed somewhere else. Because I am who I am, and have a level of neuroticism that includes paranoia, I concluded that this may have been done purposefully, that the writers had contacted me without consulting [the producers] and they ordered them out of the room. I may be wrong; I never got the full story." 
Another narrative featuring Chekov was worked on by Story Editor Naren Shankar, with a view to potentially producing it for the show's seventh season, before the idea was finally dropped. (Star Trek: The Official Starships Collection, issue 42, p. 12) Shankar later commented, "It never went anywhere. I was working on a Chekov story where he returns as a prisoner-of-war from a planet where he was imprisoned for many years and finally released. Now he has come back as an ambassador to help the Federation open up diplomatic relations, like Vietnam, essentially. The story was going to be about Worf and Chekov, because they're both Russian and Worf has heard about him and they kind of strike up a relationship together. Throughout the course of the negotiations with these people, it appears as though Chekov is sabotaging them. It turns out he is plotting to use the Enterprise to lay waste to their capital for revenge and to screw things up for the Federation because he feels they abandoned him and let these people torture him." (Sci Fi Universe, September 1994 issue)
"Children of the Light"
"The Crystal Skull"
Data's "family" story
A story idea which was considered for the fifth season but never produced involved Data and his "family," as it would have included his "brother", recurring character Lore, and Data's "daughter" from season three outing "The Offspring", Lal, as well as the emotion chip from fourth season installment "Brothers". In the undeveloped narrative, Lore stole Lal's body and tried to revive her with the emotion chip. 
"Dead On My Feet"
"Dead On My Feet" was written by Richard Krzemien, draft date 19 November 1987. (The Making of the Next Generation From Script to Screen - Part Two)
- "I wrote the story in 1987 at the behest of a mutual friend of Gerd Oswald. Oswald had directed a couple of Star Trek episodes in the sixties ("The Conscience of the King", "The Alternative Factor") and I'd spoken to him while he was directing an episode of the new Twilight Zone for CBS when I visited that studio in 1986. Oswald was looking for a story he could take to Paramount for The Next Generation which he could attach himself to as the director. He read this outline but rejected it as being 'too depressing.' I told my friend that Gerd, who was then in his seventies, was obviously a man who had never come to terms with his own mortality. Gerd Oswald died two years later of cancer." (Trek: The Next Generation)
Derelict creature story
During his time on The Next Generation, David Kemper pitched a story which was described by Rockne O'Bannon as follows:
- "The Enterprise comes across a ship that seems to be derelict. Their people go on board and the ship is empty, but the walls have this kind of slime on them, which they discover is actually a creature like a hermit crab, which takes over the ship and lives within it. When it gets larger, it has to find a bigger home, so now it heads for the Enterprise."
This story was never produced, but when Kemper became a writer for Farscape, he recycled the idea, with a number of changes in the concept, and it eventually became the first season episode "Through the Looking Glass". (Farscape: The Illustrated Companion, p. 68)
"The Dream Pool"
"The Dream Pool" was a very early TNG story idea devised by Tracy Tormé. The plot was about addiction in the Federation and was influenced by Tormé having recently read the Star Trek: The Next Generation Writers'/Directors' Guide. (The Fifty-Year Mission: The Next 25 Years, p. 128; Cinefantastique, Vol. 25/26, No. 6/1, p. 84)
"The Dream Pool" was pitched by Tormé to Producer Robert Lewin. (The Fifty-Year Mission: The Next 25 Years, p. 128; Cinefantastique, Vol. 25/26, No. 6/1, p. 84) Tormé submitted the story pitch for "The Dream Pool" at around the same time as suggesting the ultimately produced episode "The Royale". (Cinefantastique, Vol. 25/26, No. 6/1, p. 84) Lewin responded favorably to the notion of "The Dream Pool". Tormé was meanwhile unaware that Lewin was struggling with drug addiction. In hindsight, Tormé speculated, "That might be why Bob liked my addiction script. My addiction show was kind of like the cocaine allegory show that sweeps through the Federation." Despite winning Lewin's support, the story also needed to be approved by Gene Roddenberry. Tormé continued, "[Lewin] asked if I would be willing to come back and tell this to Gene, and I said sure." (The Fifty-Year Mission: The Next 25 Years, pp. 128 & 130)
Tormé waited a few weeks until Roddenberry was back in Los Angeles. (The Fifty-Year Mission: The Next 25 Years, p. 128) When he received a call to say Roddenberry had returned, Tormé was in a jacuzzi with his fiancee, in Santa Barbara. Leaving his fiancee behind, Tormé drove to meet Roddenberry in Los Angeles. (The Fifty-Year Mission: The Next 25 Years, p. 128; Cinefantastique, Vol. 25/26, No. 6/1, p. 84) "The very first thing I remember him saying to me," recalled Tormé, "was, 'So, what exactly is it that you want to do with my Star Trek? [....] I was, like, 'Oh geez, I better not misstep here and say the wrong words.' So I pitched my addiction show, and Gene said, 'I really don't want to open up that can of worms of addiction.'" Even though he didn't welcome the story, Roddenberry offered Tormé the opportunity to become a writer for the series nonetheless, which Tormé accepted. (The Fifty-Year Mission: The Next 25 Years, pp. 128 & 129)
"Elvis meets the Enterprise"
"Elvis meets the Enterprise" was a spec script which was submitted to TNG. Larry Nemecek wrote that the script was "obviously aimed at one of [Ronald D.] Moore's weaknesses." (Star Trek Monthly issue 5, p. 11)
Lisa Klink, who later went on to write stories for Star Trek: Deep Space Nine and Star Trek: Voyager, started her association with the franchise by pitching a speculative script for The Next Generation, under the open submissions policy. The script was called "The Empath" and Klink wrote it in 1993. 
Klink explained that, in the script, "The crew needed to get information from an alien race about how to get through a dangerous part of space. But the aliens only communicated telepathically, so the universal translator was no help. Troi couldn't understand them either."  As it turned out, Geordi La Forge, thanks to his visual implants, was the only crew member able to telepathically communicate with the alien race.  However, because the aliens were extremely emotional, this proved emotionally intense for him and "way out of his engineering comfort zone."   He therefore sought advice from Deanna Troi about how to deal with and interpret the emotional overload.  Troi tried to help the overwhelmed La Forge, while he continued receiving the technical knowledge from the aliens. (The Official Star Trek: Voyager Magazine issue 6, p. 43) Noted Klink, "My idea was to take the chief engineer completely out of his element and force him to solve a different kind of problem, leading to some reflection about why he chose to work with machines instead of people, and why his best friend was an android." 
Having learned that the Star Trek staff read all spec scripts they received, Lisa Klink sent her script to Paramount during TNG Season 7. (Star Trek Monthly issue 21, p. 12) The story was not accepted, but earned Klink an invitation to pitch for Deep Space Nine, starting her Star Trek career.  She stated about the spec script, "It was a perfectly good episode, if nothing spectacular." 
Following his work on "Transfigurations", René Echevarria was asked by Michael Piller to work on an environmental story for the show. Echevarria recalled, "I came up with something for which I wrote many, many drafts, but it never got off the ground. Towards the end of that process, he said he had a script that he wanted me to write. It involved every environmental story that people had done and seemed fairly obvious. They in fact commissioned a teleplay that was literally smokestacks, and it would have been very obvious to the audience that it was the cause of the blindness and mutations in a tribe that was kept on a little island called the Island of Tears. They were kept there, hidden from view, in order for the rest of the society to be able to maintain its mode of production, which was highly exploitive and environmentally unsound. The audience would have guessed at the end of the first act what was going on. What I came up with was a Federation colony that mined dilithium and they're natives to the planet. The twist was that what was causing the problems were these organisms that had evolved in the presence of electromagnetic fields of dilithium. Its removal was creating mutations." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 198)
"Errors of Judgement"
"Errors of Judgement" was a narrative devised by Ronald D. Moore. In this story, the Enterprise initiated contact with a species of aliens that were extremely curious about the Federation. Dissatisfied with the first few attempts to provide them with information about the organization, the aliens, who were capable of limited telepathic communication, wanted to enter telepathic contact with crewmembers from the Enterprise. What resulted was the Enterprise crew reliving "the biggest mistake of their lives." Moore suggested the plot to Michael Piller in a memo (dated 16 January 1990). That document included a bracketed paragraph, where Moore remarked, "There can easily be some sort of jeopardy in which we must reach some kind of understanding with these aliens in order to resolve a crisis, save an outpost, stop a war, etc." The memo went on to say, "The point of doing this show is not to say that our people are running around with these big problems over their heads. The point is to see what made them the people they are today. Picard & Co. have dealt with their regrets and can live with them... indeed their pain only made them stronger in the end. But I think we could make a really interesting show out of learning what drives those people and what private demons they've learned to deal with." This story seemingly inspired the episode "Tapestry". 
"Ferengi Gold" was a second season two-parter written by Gene Roddenberry. The story would have involved a combination of some of Roddenberry's favorite themes: alien worlds developing civilizations very similar to those of Earth, aliens (in this case, the Ferengi) utilizing superior technology to appear godly, attractive women appearing for no good reason, and the moral perfection of the Federation. (Star Trek Monthly issue 26, p. 27) There was temporarily rumor that Tracy Tormé was going to try to expand the story treatment for "Ferengi Gold" into a teleplay. The story was later included in the reference book Lost Voyages of Trek and The Next Generation (pp. 97-98). The concept of Ferengi posing as gods was used, years later, in "False Profits". (Star Trek Monthly issue 26, p. 27)
"Genius is Pain"
"Genius is Pain" was written by Tracy Tormé. The story was included in the reference book Lost Voyages of Trek and The Next Generation (pp. 99-100). Tormé recalled the genesis of the story; "I was on another one of my quests to create a new character for the show, so I had an idea: who would be a really interesting alien on Star Trek? And I got the idea of John Cleese. So I created an episode called 'Genius Is Pain' and it was about a race of aliens who are mathematical geniuses – they spend the first twenty or thirty years of their lives devoted to mathematics, and they're off-the-chart geniuses, they can do things that engineers can't do, the whole race. But once they turn thirty, they have a philosophy of life that all life should be devoted to bohemian pursuits, so if you invite them to your house and they feel like spray-painting a four-letter word on the wall of your nursery, they're going to do it, because to suppress it would be against their nature. I submitted the outline for 'Genius Is Pain', which was about five pages long, and one day I'm sitting in my office and [Gene] Roddenberry calls me, and he sounded lit, like he was not all there." In response to having received the outline, Roddenberry went into a very long, rambling speech that he began by saying he loved the proposed title but continued by lengthily musing about pain and pleasure. (The Fifty-Year Mission: The Next 25 Years, p. 84)
Geordi La Forge revelation
An episode that was temporarily planned centered around the revelation that Geordi La Forge was secretly the product of alien experimentation involving his mother. Jeri Taylor stated, "We wanted to make Geordi an alien. He was going to discover that his father was not who he thought he was, and his mother had an almost Rosemary's Baby-kind of thing and had been impregnated by an alien. As a result, Geordi was actually half alien and now, at his present age, his people were coming back to get him. I thought that would have given Geordi's character a lot of elaboration." (The Fifty-Year Mission: The Next 25 Years, p. 265) The idea bears similarities to a plot twist involving Harry Kim that was considered but rejected for VOY: "Favorite Son".
"The Hands of Time"
"The Homecoming" was a story conceived by Jeri Taylor for TNG Season 6 that went on to be developed for Star Trek: Deep Space Nine. The plot originally focused on a Bajoran woman who was picked up by the Enterprise. The female became Ensign Ro Laren in later versions of the story. However, every incarnation of the plot centered around the idea of a Bajoran woman who attempted to rescue the leader of the Bajoran resistance, a man who was deeply respected by the Bajorans but who had been wasting away in a Cardassian prison. Once the female finally managed to rescue him, the man turned out to be someone who had wearied of being a leader and no longer wanted to do that. Ultimately, he somehow became a hero once more.
When Michael Piller attempted to adopt the story for Deep Space Nine's first season, Jeri Taylor initially implored him to leave the story for TNG, saying, "You can't have it – it's my story. I need it for my series." When she thereafter witnessed the story being left untouched in the development pile throughout DS9's first season, Taylor still wanted the narrative for TNG. "I went to him and said, 'Michael, if you're not going to use that story, give it back. And he said, 'No, no, no. It'll surface, I promise you.'" The plot subsequently developed into the DS9 Season 2 opener, "The Homecoming". (Star Trek: Deep Space Nine Companion, p. 76)
"The Immunity Syndrome"
"The Immunity Syndrome" was written by J.D. Kurtz. It was completely unrelated to TOS: "The Immunity Syndrome". The story was included in the reference book Lost Voyages of Trek and The Next Generation (pp. 78-80).
Jack Crusher script
One of the three TNG spec scripts written by Mike Sussman centrally featured Jack Crusher. Sussman was aware, at least in hindsight, that this was one of many undeveloped episodes dealing with that character. "What was funny, though, was that I later submitted that Jack Crusher story, separately, to apply to the Voyager internship program and got in!" Sussman exclaimed. "However, they were not interested at all at Next Gen to [put it into production]. You know, again, they were just looking at the idea. I'm sure as soon as somebody said, 'Jack Crusher,' they said, 'Not interested. What's next?'" 
Jane Espenson spec script
"The Kreen Legacy"
Klingon cranial ridges story
As the Klingons clearly underwent a physical transformation between Star Trek: The Original Series and later Star Trek productions – including the significant addition of cranial ridges – a story was devised for Star Trek: The Next Generation to account for the change. "One of the ideas I pitched," stated freelance writer Marc Scott Zicree, who wrote the TNG Season 4 installment "First Contact", "was a story that explained why the Klingons looked like Human beings in the original series, and why they looked like crustacean heads in the current series and movies. [Producer] Burt Armus wanted to buy it, but was gone before he could." (Star Trek Magazine issue 172, p. 60) It was ultimately not until the two-parter "Affliction" and "Divergence", in the fourth season of Star Trek: Enterprise, that the noticeable differences in the two styles of Klingons was explained.
Larry Brody script
TAS and VOY writer Larry Brody wrote a script for Star Trek: The Next Generation, towards the end of the first season. According to Brody, the subject of the episode's original title was essentially "all about being a dreamer." He was given the task of writing a TNG script by Gene Roddenberry. "Gene called my agent and said he was in a bind and needed a quick script from me," said Brody, "one that could be written and ready to produce before an impending writers' strike." Roddenberry was stockpiling scripts in case the strike lasted for a long time. Because Brody was worried about saving enough money to pay for a new mortgage he had taken out, he agreed to the offer. (The Fifty-Year Mission: The Next 25 Years, pp. 128-129)
Next, Brody and Roddenberry collaborated to work out the story idea. "I wrote the outline in a couple of days, but instead of hearing directly from Roddenberry about it, I was called by Maurice Hurley," Brody continued. "He called me in to meet about the story to get his notes about going to script. While I was there, Roddenberry's office buzzed Hurley and asked him to send me over to see Gene when Hurley and I were through." At Roddenberry's office, Brody was shocked at how lacking in energy Roddenberry seemed to be, how vague his conversation was, and how much difficulty he had with focusing on things. Roddenberry was meanwhile holding Brody's outline, though it became clear that he hadn't read it nor could even remember at all what the premise was, even though he and Brody had devised it together. For approximately ten minutes, Roddenberry talked about how meaningful the title was, describing all writers as "dreamers." Brody later noted, "The meeting was cut short. I don't remember why. It turned out to be the last time I saw or talked to Gene." (The Fifty-Year Mission: The Next 25 Years, p. 129)
After Brody returned home, he wrote the script. He then submitted it to Paramount, although he didn't hear any response to it until a few weeks later, while the anxiety-inducing 1988 writers' strike was well underway. At that point, Brody received a final draft, which had a new title and had been revised by Maurice Hurley. It became clear to Brody that something was wrong. "That became even clearer," stated Brody, "when Bob Justman, the line producer of the show and a guy who was closer to Gene than anyone, sent me some memos he'd written about the script, detailing what he thought its strengths were. Along with the info that it was being shelved for reasons he couldn't give." (The Fifty-Year Mission: The Next 25 Years, p. 129)
"Leap of Faith"
"Leap of Faith" was one of the multiple stories that Fred Bronson and Susan Sackett conceived and pitched to Michael Piller for the third season. "[It] involved Deanna Troi getting stuck in Time on a planet," said Bronson, "and living a whole second life where she had children. But Michael said 'No I don't [think] that works!'" The tale was uncannily similar to fifth season award-winning installment "The Inner Light". However, Bronson believed he and Sackett wouldn't have been able to make "Leap of Faith" any better than "The Inner Light" turned out. (Starburst, Special #29, p. 56)
"The Lost and the Lurking"
"The May Fly"
"The May Fly" was written by Richard Krzemien, draft date 1 October 1987. (The Making of the Next Generation From Script to Screen - Part Two)
Mike Sussman's Klingon show
The first of Mike Sussman's three TNG spec scripts featured a Klingon-centric story. He wrote the script in about 1989 and/or early 1990, after the making of TNG: "Heart of Glory" but before "Sins of the Father". Sussman later reflected, "I'm like, 'I want more Klingons!' So, I wrote a spec script involving Klingons [....] They probably got, you know, five of those a day." Sussman sent the screenplay into the studio, only for a trailer advertising "Sins of Father" to be shown on the following day, revealing to Sussman that that episode's writer, Ronald D. Moore, had somewhat frustratingly "beat [him] to the punch." Sussman ultimately thought his undeveloped Klingon story "was just not very good." 
Mirror universe stories
Multiple narratives set in the mirror universe, established in TOS: "Mirror, Mirror", were suggested for Star Trek: The Next Generation. "We've been pitched 'Mirror, Mirror' sequels since The Next Generation began, and I wasn't interested," admitted Michael Piller. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 74)
As early as 21 February 1987, a mirror universe episode was mentioned as having been proposed for TNG; on that date, David Gerrold jokingly reported that, in the only TOS sequel which had so far been suggested for TNG, "The Enterprise returns to the 'Mirror, Mirror' universe and Edith Keeler is eaten by carnivorous tribbles." (Starlog, issue #119, p. 21)
Even Jerome Bixby, who had written "Mirror, Mirror", wrote and submitted a TNG sequel to that episode. (Starlog, issue #164, p. 45; Starlog, issue #167, p. 5) The story he suggested featured not only the mirror universe but also members of the TOS crew. The episode was rejected because Paramount Pictures wanted mostly to stay clear of those characters in TNG. (Starlog, issue #167, p. 5)
"The Mnemonic Enemy"
"The Mnemonic Enemy" was one of the stories that Fred Bronson pitched to Robert Lewin for the first season. It was a story that addressed gender and, during the events of the tale, the females aboard the Enterprise became separated from the ship's male contingent. Lewin was extremely interested in this narrative and liked it, but it needed to be approved by the other TNG producers too. When he and Bronson met for the second time, Lewin revealed that "The Mnemonic Enemy" might not be produced because it was too similar to a story which the producers were meanwhile considering. Since they couldn't do both, Lewin was attempting to persuade the others to do Bronson's tale. Eventually, however, this narrative was rejected in favor of the other one, which was ultimately produced as the first season episode "Angel One" and had a different story to this tale, although both dealt with the concept of gender. The rejection of his story somewhat frustrated Bronson, but he remained determined to write for the series, and he was finally granted that aim when he co-wrote (with Susan Sackett) "Ménage à Troi" and the story for "The Game", in the third and fifth seasons respectively. (Starburst Special #29, pp. 55-56)
Ronald D. Moore pitched the idea of doing a musical episode on Star Trek: The Next Generation. He thought this notion was "great" but no other staff writers wanted to do it. Though mention of the concept years later elicited a laugh from Brannon Braga, both he and Moore agreed that, with use of the holodeck, the episode could indeed have been produced. (All Good Things (Blu-ray) audio commentary)
"My Inky Cloak"
"My Inky Cloak" was written as a spec script by freelance writer Darrell James, and was logged in on 13 October 1992. The script's title was taken from a line of dialogue in the William Shakespeare play "Hamlet".
"The Neutral Zone"
An unproduced Romulan story, also featuring aspects that made their way into "Too Short a Season", was entitled "The Neutral Zone". It was completely unrelated to the later "The Neutral Zone". Scripted by Greg Strangis, the story featured famous Starfleet security expert Billings, who, confined to a wheelchair and clearly distant and lonely, had led the mission which had rescued Natasha Yar from her brutal homeworld. Yet, in spite of Yar making efforts to better make his acquaintance, he was completely oblivious to her attempts. Billings' mission was revealed in short order: the Enterprise was to take part in a trade negotiation which would involve, for the first time, the Romulan Empire. Picard's mission would be to get the Romulan delegates there, and Billings was on hand to ensure that all went well.
To implement this, he compiled a list of all Enterprise personnel who had had contact with Romulans, and ordered that they be dropped off at a starbase for the duration of this sensitive mission. Ironically, this group included the inveterate Romulan-hating Worf, whom Picard then defended; Worf managed to remain on board, where he became involved in a subplot additionally focusing on Wesley Crusher. Meanwhile, Doctor Beverly Crusher proposed an operation involving fluid drawn from Data's spine to help Billings, who brusquely declined.
Romulan commander Gar, obviously against the accord he had been assigned to promote, beamed aboard and dissension ensued. Matters grew complicated when the transporter malfunctioned while the rest of the Romulan delegation was beaming over; after some tense moments, they were safely returned to their own ship, but Gar was less than pleased, especially when Data discovered a sabotaging device inside the transporter console.
Unfortunately for Wesley Crusher and Worf, their separate subplot took them, without authorization, into the transporter room; this did not bode well for them, until Tasha turned up with security tapes, showing Gar inserting the device. The Romulan remained insouciant, claiming that the negotiations had been leading to disaster anyway and that his actions had merely been getting the problem out of the way quicker. With all this sorted out, Billings consented to Dr. Crusher's proposed operation, and was thereafter able to walk. (Trek: The Unauthorized Behind-The-Scenes Story of The Next Generation)
In the story, Picard made a passing reference to an engagement with a Romulan ship sometime in his career. Notably, this account was inconsistent with the history of Romulan isolation as described in the produced episode "The Neutral Zone".
"No Room at the Inn"
"Once a Klingon"
"Once a Klingon" was written by D.C. Fontana and Herbert J. Wright. It was a developmental precursor of the first season episode "Heart of Glory". The first draft story outline for "Once a Klingon" was submitted on 4 November 1987.
In a one-page memo he sent Gene Roddenberry (on 7 November 1987), Robert Justman commented that, although he approved of the story, it seemed to him like it might be expensive. Therefore, he listed four of the episode's aspects that most concerned him financially, which were: the necessary visual effects; the special makeup involved in portraying the Klingons; guest cast overtime; and set construction. 
"The One and Lonely"
"The One and Lonely" was written by Richard Krzemien, draft date 18 June 1987. (The Making of the Next Generation From Script to Screen - Part Two)
"One Little Ship" precursor
Prior to making his first script sale (the Season 3 episode "The Offspring"), René Echevarria wrote a TNG spec script about a spacecraft being shrunk and the ensuing events. It was the second spec script he wrote for Star Trek. Echevarria characterized it as "a really tiny, cute comedy." (Cinefantastique, Vol. 30, No. 9/10, p. 39) Echevarria never sent the spec script into the studio while he was freelancing, though he always kept it mind. It was only once he joined the show's writing staff as story editor, during the sixth season, that he broached the subject. Supervising Producer Jeri Taylor reacted by looking at him as if he had gone insane. (Star Trek: Deep Space Nine Companion, p. 528) Years later, however, Echevarria submitted the story to Star Trek: Deep Space Nine, then to Star Trek: Voyager, before the idea ended up being used as the basis for DS9: "One Little Ship". (Cinefantastique, Vol. 30, No. 9/10, p. 39)
"The Outer Lights"
Morgan Gendel, who wrote "The Inner Light", pitched a sequel which involved the Enterprise discovering another probe from Kataan, only this probe had three living Kataan natives in suspended animation, one of whom was Eline, a scientist who the woman from Picard's vision had been based on. Picard would have become emotionally distraught, with Eline becoming distraught that a man she's never met has strong feelings for her. Gendel pitched this story several times, but it was rejected, as Rick Berman and Michael Piller were not interested in doing a sequel to "The Inner Light". Gendel believes this was a bad decision, as he feels the story was incomplete. He later tried to revive the episode via an online comic on Trekmovie.com (The Fifty-Year Mission: The Next 25 Years, p. 265)
"Out of Time"
During the seventh season of TNG, Joe Menosky pitched a story, originally called "Out of Time", in which Alexander Rozhenko accidentally fell into a time portal and permanently aged into a bitter man. According to René Echevarria, Menosky greatly disliked the character, and saw this as a way to "get rid" of him. (Star Trek: Deep Space Nine Companion, p. 577) In the story, Worf and Alexander traveled to a planet to carry out a Klingon hunting ritual when Alexander suddenly disappeared. (Cinefantastique, Vol. 25/26, No. 6/1, p. 87; Star Trek: Deep Space Nine Companion, p. 577) Echevarria continued, "Worf loses sight of his son for a second. Alexander goes through some kind of portal, winks out, and then a second later he walks out." (Star Trek: Deep Space Nine Companion, p. 577) Jeri Taylor recalled, "Worf looks around and calls out for him. A second later Alexander's voice answers 'Here I am.' Worf looks up and there is Alexander, now a scarred, battle-hardened [man] [....] Through various sci-fi reasons he was winked to another kind of dimension and was deposited there as a nine year old in a very harsh cruel environment, sort of a Mad Max kind of place where he had to fight and survive without anybody or anything. To him, he lived [...] years more in this really rotten environment, abandoned in a sense by those who loved him, and turned into this battle hardened kind of warrior." Taylor additionally described the duration of Alexander's stay in the other reality as "9 years," resulting in him returning as an "18 or 19 year old." (Cinefantastique, Vol. 25/26, No. 6/1, p. 87) According to Echevarria, though, Alexander spent "fifteen years" in the other world. Echevarria went on to note, "He's now a grown man and a warrior and he has great resentment toward his father because he doesn't understand what happened." (Star Trek: Deep Space Nine Companion, p. 577) Taylor explained, "In a blink of [an] eye Worf has lost his son and his son has lost his childhood and now they go back onto the Enterprise with somebody no one is prepared to deal with." (Cinefantastique, Vol. 25/26, No. 6/1, p. 87)
Michael Piller repeatedly quashed the story idea. Ronald D. Moore noted, "Michael shot it down time and time again." According to Echevarria, "We never did that show because Alexander was Michael Piller's mother's favorite character." (Star Trek: Deep Space Nine Companion, p. 577) Piller himself offered, "I just thought it was a nasty thing that we were basically taking the kid's entire childhood away. I just wouldn't go for it." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 303) Jeri Taylor concluded, "I thought it was a dynamite story and always wanted to do it and Michael just wasn't comfortable with it for a lot of reasons. It's the one story I regret we didn't do [on TNG]." (Cinefantastique, Vol. 25/26, No. 6/1, p. 87)
While the premise remained unused on TNG, it inspired the idea of having a time-traveling Alexander in "Firstborn". (Star Trek: The Next Generation Companion 2nd ed., p. 292) Echevarria kept the story in mind after moving to Star Trek: Deep Space Nine, and it was eventually developed (after much resistance from Ira Steven Behr) into the sixth season episode "Time's Orphan", with Molly O'Brien in place of Alexander. (Star Trek: Deep Space Nine Companion, p. 577)
"Past Lives" was a story devised for TNG Season 2, by writing partners Fred Bronson and Susan Sackett. It was the first story they paired up to write, which they did after realizing both of them had been pitching stories which had kept being rejected. Regarding the subject of past lives, Bronson stated, "[It] at the time was unexplored territory, but now would sound old hat." He went on describe the tale; "It involved a woman from the Future coming back, and accidentally causing the death of Captain Picard, and them having to fix that damage in Time. And it involved Romulans and Klingons."
Fred Bronson and Susan Sackett managed to sell the story of "Past Lives" to Gene Roddenberry. However, Maurice Hurley wasn't particularly interested in it. Though Hurley soon departed the series and the consequently vacant staff position was filled by the arrival of Michael Piller, the story was likewise disliked by Piller, so it was never produced. (Starburst, Special #29, p. 56)
Perchance to Dream script
A spec script that Howard Weinstein wrote and submitted to Star Trek: The Next Generation ended up becoming the basis for his novel Perchance to Dream. "They didn't buy it," he explained, "but Michael Piller thought enough of the script to extend an invitation for me to pitch other stories [....] I still think it would have made a neat TV episode." (Voyages of Imagination, pp. 173-174)
A Star Trek: The Next Generation story idea which was originally titled "Profit Margin" and was pitched by Hilary J. Bader involved a female Ferengi, named Pel, posing as a male of the species. "I had Pel involved with Riker to begin with, and then had Beverly Crusher find out, and some kind of sisterhood relationship developing," Bader recalled. The concept later became the basis for "Rules of Acquisition", a Ferengi episode of Star Trek: Deep Space Nine. (Star Trek: Deep Space Nine Companion, p. 96)
Season 5 Q stories
During the fifth and early sixth seasons of The Next Generation, the writing staff struggled with two premises using Q that were both ultimately rejected, leading to an unintentional season-long absence of the recurring antagonist.
"Q Makes Two"
In "Q Makes Two", Q would have duplicated the Enterprise and the crew according to some uniform characteristic. Brannon Braga explained, "Q comes on board and Picard's saying people are inherently good and we have managed to get rid of our darker elements in the 24th century and we're better people. Q says, 'So you don't think you have dark components and you think you're better without them, well I'm going to show you a thing or two,' and so he extracts the darker components and puts them into doubles. The clean, good components suffer and so do the darker components and neither functions without the other. We see that dramatically [....] The image in my mind that we never really got to was the two Enterprises shooting at each other, that's what you want to see." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 263) However, René Echevarria clarified that, after duplicating the Enterprise crew, Q did have the two crews confront each other. (TV Zone, issue 62, p. 28)
The evolution of "Q Makes Two" was troubled. Brannon Braga recalled, "There was a sense of doom from the moment we started 'Q Makes Two'. I think we broke it three times. René [Echevarria] wrote two drafts." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 263) Echevarria himself described the story as "the bane of the staff's existence," and specified that it had been bought and was in development by the time he began working on it. He went on to say, "[Executive Producer] Jeri [Taylor] said, 'These are the four or five ideas we have rolling around; which one appeals to you?' and foolishly I said that one. I wrote a first draft that Michael [Piller] said wasn't workable, and we ran it by him three times before he finally approved the teleplay. From a production standpoint, we had to ask ourselves, 'How produceable is this?' Almost every scene would have to be done as an optical, and it wasn't practical, and Michael said the story wasn't working practically dramatically. That story was killed." (TV Zone, issue 62, p. 28) Brannon Braga agreed, "It was ultimately abandoned. It's an interesting notion [...] but for some reason we made it more complex than it needed to be. It's a show that could still work." Jeri Taylor added, "'Q Makes Two' was a debacle and it plunged us into a nightmare of having to get 'Man of the People' ready." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 263)
The dismissal of this episode made way for the episode "True Q". (TV Zone, issue 62, p. 28) According to Taylor, the idea of splitting a starship in two later inspired the Star Trek: Voyager episode "Deadlock". (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 166) The plot also notably resembles the original series episode "The Enemy Within", except with the entire crew duplicated, rather than just the captain.
In the other scrapped premise, entitled "I.Q. Test", Q would have had a wager against another member of the Q Continuum that would have led to a deadly contest between the crew and the Zaa-Naar, a dangerous alien race. (Star Trek Monthly issue 26, p. 27) In fact, Q would have used the crew in a sort of Olympics against the other Q, and the Zaa-Naar would have been the other Q's chosen race of supermen. (AOL chat, 1998) The episode was based on a story by a new writer and involved input from Herbert J. Wright. (Star Trek Monthly issue 26, p. 27) A first draft script, which was credited to Wright alone (specifically for the teleplay), was issued on 10 January 1992.
Despite rumors that Arnold Schwarzenegger would have appeared in the episode, Ronald D. Moore clarified, "There was never – ever – any chance that Arnold was going to appear on the show." (AOL chat, 1998)
Q goes insane story
Ronald D. Moore devised a story which had Q losing his mind. "I pitched a memo about a Q show," he recalled. "The universe suddenly fractured, and there were all these bizarre things happening." (Star Trek: The Official Starships Collection, issue 42, p. 13) Moore elaborated, "It was a totally nutso beginning – Picard is suddenly walking down [a] New York street dressed in his uniform but carrying a brief-case and wearing a fedora. He passes Riker who is pounding on the side of a building with a loaf of bread – that's Riker's job, to pound the side of a building with a loaf of bread. And a Klingon driving a taxi cab drives by and a knight in shining armor is the cop, all this insane stuff." (Cinefantastique, Vol. 25/26, No. 6/1, p. 86) In fact, Moore imagined multiple armor-clad knights walking around on the New York street. (Star Trek: The Official Starships Collection, issue 42, p. 13) "All our characters are there and they are doing things that make zero sense," he continued, "and then the camera pans by an alley and there lying by a trash can is Q who is dressed like a homeless guy and he is mumbling to himself 'I used to be a super-being' [....] It's all about us trying to figure out that none of this is the way things are supposed to be and that nutty guy who is saying he used to be a super-being is actually right." (Cinefantastique, Vol. 25/26, No. 6/1, p. 86)
Though it had its supporters among the creative staff, the story wasn't greenlit for production because the producers vetoed it. In retrospect, Ronald D. Moore described the plot as "The one great one that I think the whole writing staff loved, but could never quite talk them into doing [....] We were totally nuts, but we said 'Man, this would be so cool.'" (Cinefantastique, Vol. 25/26, No. 6/1, p. 86) Despite the story being rejected, it notably inspired Michael Piller. "Michael didn't really buy it," Moore clarified, "but he did pick up on it and say that we should bookend the series with a Q show." Hence, the story directly influenced the writing of TNG series finale "All Good Things...". (Star Trek: The Official Starships Collection, issue 42, pp. 13-14)
Quantum Leap Q story
At one point, Robert Hewitt Wolfe pitched a Q story much in the style of the series Quantum Leap. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 45) Wolfe specified that he pitched it "when I first came to TNG." (Cinefantastique, Vol. 27, No. 4/5, p. 95) During the course of the story, Q transformed Picard, Data, and Deanna Troi into officers aboard a Romulan ship. "There was no Romulan makeup involved; they weren't possessing the bodies," explained Wolfe. "The visual gag was the same as Quantum Leap, where we would look at them and see them as themselves and maybe in a reverse shot we might see them as other people completely." The degree of similarity to Quantum Leap caused the producers not to want to do the story, which consequently was never bought. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 45) Wolfe considered TNG: "Face of the Enemy", however, as similar to his undeveloped plot. (Star Trek: Deep Space Nine Companion, p. 177) Moreover, the story served as a conceptual precursor to a particular undeveloped episode of Star Trek: Deep Space Nine and, ultimately, the DS9 episode "Second Skin". (Cinefantastique, Vol. 27, No. 4/5, p. 95)
A story concept Ronald D. Moore loved and wanted to do was a backwards episode, featuring a reverse chronology. As Moore later explained, the planning of the story was "where [it was said], you know, 'Okay, some time thing happens where we're gonna move backwards through the episode, somehow.'"
The writing staff endeavored to develop the story. "We never could crack it," Moore recalled. "I remember us trying to crack it and talking about it [....] I might have even tried to break an episode like that, once [....] We couldn't come up with the structure of it and how it would work mechanically." Moore was desperate to "find some hook into it," in his words.
The reverse story idea ultimately disappointed Moore. "I was so frustrated," he said. As a result, Moore conceded, "For me, [it was] the great white whale," referencing Captain Ahab's quest for the ever-elusive whale named Moby Dick in the story Moby Dick. It was not until the Star Trek: Voyager episode "Before and After" that a backwards episode of live-action Star Trek was achieved. Years after struggling with the plot concept for TNG, Moore was impressed by seeing the Seinfeld backwards episode "The Betrayal". (All Good Things (Blu-ray) audio commentary)
"Return to Forever"
"Return to Forever" was a two-part story whose conception was related to Tracy Tormé becoming one of the few members of the TNG writing staff who was persuaded to return for the show's second season; the opportunity to write the story was offered to Tormé as an enticement to stay with the series. As presented to him, the story was a two-parter involving Leonard Nimoy as Spock. Tormé devised the plot as a sequel to TOS: "The City on the Edge of Forever", reusing the Guardian of Forever. "I thought it might be fun to bridge the old show now that we'd had a season under our belt," he explained. "I thought about the old Harlan Ellison episode [....] What I had going was that a small research team was allowed to work with this thing [the Guardian] and were all found dead and Spock ended up coming through from the past. There was a circular story where I had two Spocks on the ship at the same time, one was in a coma and the one from the present was still alive. The reason the Spock from the past came through was all tied into the one in the present, yet the one in the present didn't have any memory of this. Then at the end, the present Spock puts his hands against the past Spock and tells him to forget, so he goes back in time not remembering that he will meet himself." Regarding the story's fate, Tormé concluded, "It never got past outlining, because something fell out with Nimoy." (Cinefantastique, Vol. 25/26, No. 6/1, p. 85)
The story that eventually became "Captain's Holiday" started out as a mostly unrelated script by Ira Steven Behr and Ronald D. Moore, where the Enterprise stops for shore leave at the pleasure planet Risa, and Picard finds a sideshow attraction which shows the customer their greatest fear. In Picard's case, this fear manifests as a vision of a possible future in which he is an admiral with an unfulfilling desk job, with Riker now the captain of the Enterprise. Though the script got quite far into the writing process, Gene Roddenberry ultimately ordered that it be dropped, as a person having fears and doubts about the future didn't fit his vision of 24th century Humanity.
Despite the story being junked, several plot elements later found their way into other TNG-related works. Roddenberry liked the concept of Risa enough to ask Behr to write a new story where the planet was the primary setting (having just provided the framing story in the earlier script), while the idea of a future where Picard is an admiral and Riker captain of the Enterprise was used the following year, in "Future Imperfect", and Moore made Picard's wish to remain a starship captain well into his latter years a plot point in Star Trek Generations. ("Technological Distinctiveness", TNG Season 3 Blu-ray special features)
Actor-writer Geoffrey Thorne wrote an unproduced episode of TNG, "The Rivals",  not to be confused with a similarly titled episode of DS9. Although this did not get produced, Thorne later succeeded in writing official Star Trek tie-in novels.
Ro Laren murder story
The story that became DS9: "Little Green Men" was originally pitched for Star Trek: The Next Generation. In its original conception, it would have had the Enterprise in pursuit of four Ferengi who had traveled to the mid-1900s and crashed. Their bodies and ship were recovered by the United States military, leaving the Enterprise to clean up. The pitch was well-received by René Echevarria, but not used because he wanted just a single time travel story per season, and one was already in the works. Five months later, the story was successfully re-pitched for Star Trek: Deep Space Nine, using Quark, Rom, and Nog. 
Sarek and Spock story
A story that D.C. Fontana and Herbert J. Wright pitched, during TNG's first season, would have featured Spock, Sarek, and Romulans. Fontana detailed the specifics of the proposed plot, which had some similarities to the ultimately produced two-parter "Unification I" and "Unification II"; "We're taking on a mysterious Vulcan visitor who, of course, turns out to be Spock, and his mission is to rescue his father, who has been captured by the Romulans while on an exploratory peace mission. Now he's being held hostage, and they want Spock." Fontana was told that the plot was not granted production approval due to the unlikeliness of obtaining either Mark Lenard as Sarek or Leonard Nimoy as Spock. (Star Trek: The Magazine Volume 1, Issue 2, p. 87) According to Herb Wright, the reasoning was that Nimoy had "a falling out" with Gene Roddenberry and instead directed Three Men and a Baby. Wright noted of the story, "I thought [bringing Spock back] would have been great first season." (Cinefantastique, Vol. 23, No. 2/3, p. 48) Fontana spoke more about the story in TV Zone magazine (issue 51, p. 25).
"See Spot Run"
"Shattered Time" was written as a spec script by Eric A. Stillwell. He wrote it during a hiatus between the first and second seasons. Stillwell finished writing the script during a writer's strike in 1988, while he was working as a production assistant on TNG. (The Making of Yesterday's Enterprise, pp. 22 & 38) The first draft of the script, containing fifty-eight pages, was dated 8 August 1988. In Stillwell's own words, the story was "an allegory about the consequences of a misguided missile defense program – adopted by an advanced alien civilization." (The Making of Yesterday's Enterprise, p. 38)
"Shattered Time" won the approval of Maurice Hurley, who was meanwhile running the TNG writing staff, while Gene Roddenberry was the overall showrunner. Production Manager Sam Freedle and, shortly thereafter, Paramount television executive Tim Iacofano both asked Stillwell if they could read the script, and they both liked it. Meanwhile, Hurley had passed a copy of the document to Roddenberry, who had final say as to whether the script would be bought and produced. "It seemed like an eternity passed before Roddenberry got around to reading my script," Stillwell recalled. When he finally read it, Roddenberry, without any explanation or feedback about the document, rejected the script, news which Hurley later relayed to Stillwell. When Michael Piller became the head writer at the start of the third season, Stillwell chose to submit "Shattered Time" as a writing sample. Unfortunately, the script had been written in a style more suitable for the first season than the third season, by which time it was somewhat dated. Nonetheless, Piller still read the script. "His response was very generous, but clear: it wasn't the kind of script he was looking to produce during the third season," concluded Stillwell. (The Making of Yesterday's Enterprise, pp. 38-39)
"Ship in a Bottle" sequel
A follow-up to "Ship in a Bottle" was planned, wherein Moriarty would discover he was trapped in a virtual world and would entreat Data to enter with a distress signal. (The Fifty-Year Mission: The Next 25 Years, p. 277)
Sigma Iotia II story
During TNG Season 7, Ronald D. Moore wanted to write a story about the Enterprise-D visiting the planet Sigma Iotia II, previously established in the Star Trek: The Original Series outing "A Piece of the Action". In the story, the Iotians were found to currently be imitating James T. Kirk and his crew, rather than 1920s gangsters. (Star Trek: The Official Starships Collection, issue 42, pp. 12-13, 14)
The story was revisited as one of the concepts investigated for a 30th anniversary show on Star Trek: Deep Space Nine and was ultimately done as a story in the final issue of Marvel's Star Trek Unlimited, "A Piece of Reaction".
"State of Mind"
"Somewhen" was written by Vanna Bonta.
The USS Enterprise-D received a distress call from the transport ship Pleides, which had been caught in the Docleic Triangle, a space version of the Bermuda Triangle. The Enterprise followed the distress call and went into this area of space, which was filled with several energy rings. While passing each energy ring, a different time continuum was created. The changes during these leaps in time included a living Jack Crusher, who served as first officer to a beard-wearing Captain Jean-Luc Picard and a different Geordi La Forge, who was able to see, had a wife and three children, and had never joined Starfleet.
Data was the only crew member who realized all these changes and convinced Captain Picard that the Enterprise should leave this area of space because of a nearby ion storm. Aboard the Pleides, no-one answered the Enterprise's hails. While traveling back through the leaps of time, Doctor Beverly Crusher decided to stay in one of the created alternate timelines, and Wesley Crusher was consequently never born. Captain Picard convinced Dr. Crusher to return with the crew, and the Enterprise finally went back to the original timeline. (Das Star Trek Universum, Band 2)
Prior to "The Storyteller" becoming an installment of Star Trek: Deep Space Nine, Kurt Michael Bensmiller scripted it for Star Trek: The Next Generation and submitted the teleplay to the TNG writing staff during the show's first season. "I think it was similar to something they had under development," stated Bensmiller, "so they didn't go ahead with it but instead asked me to pitch some other ideas." Nonetheless, the script for "The Storyteller" remained in the TNG offices. (Star Trek: Deep Space Nine Companion, p. 47) After Michael Piller joined the staff in the show's third season, he read the script and liked it, buying the pitch and subsequently keeping it in mind until the time came when he could use it for DS9. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 33; Star Trek: Deep Space Nine Companion, p. 47) Piller recalled, "I had this script in my desk for three years and I bring it out every season and I say should we do this script this year? Everybody reads it and they say let's not do it. They just didn't like it." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 33) Bensmiller concluded, "For a variety of reasons, it never got made for TNG." (Star Trek: Deep Space Nine Companion, p. 47)
The first of two never-produced stories which Ron Wilkerson and Jean Louise Matthias sold to TNG was a sequel to the episode "Tapestry". In the story, Captain Picard attended the reunion of his Starfleet Academy class, where he was reunited with Marta Batanides and Cortan Zweller. Having become a less-than-excellent starship captain before recently resigning, Zweller was embittered at the reunion, where Picard was contrastingly "the star." "So here they were coming back to face each other and there is a great amount of pressure to perform for your friends," related Matthias. Wilkerson added, "Corey wanted to involve Picard in a new scheme and Picard realized he could help his friend, but only by taking a risk, putting himself on the line for friendship."
This story achieved considerable success before being discarded. Wilkerson remarked, "It was a rather good Picard episode [...] because you get to see him react to a friend who hasn't done as well as he has. Jeri [Taylor] seemed to like it, but eventually Michael [Piller] decided he didn't want to do it. We got paid, but nothing happened." (Cinefantastique, Vol. 25/26, No. 6/1, p. 87)
"Terminus" was a story written by Philip and Eugene Price, revised by Robert Lewin and Dorothy Fontana. It remained in story-outline form but featured a character that was later re-conceived as Lore. The story was included in the reference book Lost Voyages of Trek and The Next Generation (pp. 70-72).
"To Thine Own Self Be True"
"To Thine Own Self Be True" was a first draft spec script written by Julie King, from a story by Julie and Karen King. The script was dated 17 September 1989. However, it was under option for TNG until its seventh and final season.  The script itself is available to read on Julie King's website .
Troi's command episode
Early in the first season, a story idea that was thought up and discussed would have featured Deanna Troi having to take command of the Enterprise because, as phrased by Troi actress Marina Sirtis, "the entire military side" of the Enterprise's senior staff had been "incapacitated." Sirtis prevented that plot from developing further. Shortly after the story concept was devised, she recalled, "I told them no way. I'm the mental person. Deanna would be dangerous with that kind of power." (Starlog, issue 126, p. 58) Ultimately, it wasn't until the TNG Season 5 episode "Disaster" that Troi had an experience of having to take command of the Enterprise.
"Two Yuffs Two Many"
"Two Yuffs Two Many" was written by Richard Krzemien, draft date 9 July 1992. (The Making of the Next Generation From Script to Screen - Part Two)
A story idea which was often proposed involved the advent of a cure for Geordi La Forge's blindness, negating the use of his VISOR. This concept was featured in the second of two stories which Ron Wilkerson and Jean Louise Matthias managed to sell to TNG but which never progressed beyond the story phase of development, though the idea was included in an anti-time future setting in TNG series finale "All Good Things...". (Cinefantastique, Vol. 25/26, No. 6/1, p. 87)
Water planet story
An idea for an episode featuring a water planet was suggested by Nelson Gidding, who was the first writer invited to pitch for the series. The story idea was personally submitted by Gidding to the TNG writing staff, firstly in a pitching session that didn't include Gene Roddenberry. "What we get is this slightly befuddled old man who starts talking to us about pricklys and gooeys, that some people in the world are prickly and some are gooey, and he wants to do a water planet where the people make love by getting in a hot tub together. The man has been living in California too long," recalled David Gerrold. "Then he goes on to pitch for an hour and it's making no sense at all. I looked at Eddie Milkis to see his reaction, and he is absolutely blank-faced. I look at Bob [Justman] and he's absolutely blank-faced. I go back to making notes dizzily. Later on, Eddie said to me, 'Don't ever do that again. You gave me such a look that I nearly burst out laughing.'" Though Gerrold believed they should call Gidding's agent and profusely thank him but then decline the concept, those who had listened to the pitch didn't have the authority to reject the story idea, as Roddenberry had to hear it before it could be refused. Gidding, despite Gerrold objecting, was later called back to pitch the story while Roddenberry was there. Though Gidding enthusiastically recited the concept at the second meeting, the pitch was then finally declined, having wasted much of the writing staff's time. The story idea was the only one which Gidding submitted for the show. (The Fifty-Year Mission: The Next 25 Years, p. 69)
Watts riots story
A plot once suggested by Robert Hewitt Wolfe involved the Watts riots of 1965. "I pitched a story to TNG where Geordi and Picard crash-lands in Watts right before the riots," said Wolfe. Though this concept was never developed for TNG, Wolfe found the idea was influential during the writing of third season Star Trek: Deep Space Nine two-parter "Past Tense, Part I" and "Past Tense, Part II". (Cinefantastique, Vol. 27, No. 4/5, p. 92)
Wesley Crusher's alien girlfriend
A "gay-themed" episode was proposed by Rene Echevarria for the sixth or seventh season where Wesley Crusher has a friend named Los from Starfleet Academy, who stood by him during the incident in "The First Duty". During the episode, Los, who is very close to Wesley, changes gender (his species is able to do so biologically) to become closer to Wesley. The twist is that Los' species can only be the opposite gender for a few hours at a time. Rene Echevarria wanted the episode to explore complex gender and sexual themes, in particular LGBT themes, but this is probably why the pitch was rejected. The name "Los" is similar to "Laas", a character from "Chimera", which is another episode that Echevarria wrote. (The Fifty-Year Mission: The Next 25 Years, p. 277; )