The first unproduced story idea for an episode of DS9 was devised during an approximately five-day brainstorming session between Ira Steven Behr and Peter Allan Fields during the week of 15 June 1992, which led them to devise the premises for the first-conceived episodes of DS9 Season 1 (apart from the pilot episode "Emissary"). Behr commented that this idea simply "did not fly." However, there were fewer undeveloped story ideas that he and Fields conceived during that period than the ones which did actually get made. (The Fifty-Year Mission: The Next 25 Years, pp. 422 & 423)
By comparison, there were many never-produced episode concepts which were submitted by freelance writers. Clarified Robert Hewitt Wolfe, "DS9 got dozens of pitches a week and we turned down 99% of them, but it was rare that something went to story then died." 
The system whereby lots of never-produced story ideas were submitted by freelance writers was begun early in the series' development, before DS9 had even premiered. As a consolation, Ira Steven Behr stated, "I would like to take everyone out who has tried to write a story, written a story, got hired to write a story and got cut off on a story and buy them dinner. It's like, into the valley of death rode the six hundred. These people took a wing and a prayer, some of them went off before we cast the show, while the sets were being built, and all they had to read was this pilot with all these new characters and a new environment that none of them knew. It's tough to hit a home run under those circumstances as a writer. I would not like to have tried it." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 29)
Many never-produced DS9 story ideas involved large-scale conflict. During the making of the series, René Echevarria stated, "People often come in and pitch Klingon and Cardassian wars – something big that we probably are working on ourselves." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 116)
Many writers unsuccessfully tried to write and pitch a story about Morn; virtually everyone who attempted to write about him was stymied by the fact that he never spoke on-screen. (Star Trek: Deep Space Nine Companion (p. 523)) Other undeveloped stories involved the character of Iliana Ghemor, from DS9: "Second Skin". "I've heard several pitches where people want to find [her] [...] so obviously quite a number of people were struck by [the episode]," commented René Echevarria. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 85)
Writing duo and sisters Barbara J. Lee and Jenifer A. Lee pitched, to René Echevarria, approximately seventeen unused stories in an hour-long pitch session. Echevarria listened to them all, though initially "there was nothing interesting," he remarked. During the course of the session, the narratives suggested by the Lee sisters varied from the relatively elaborate to one-liners, in that order. Echevarria decided not to pick any of the ideas until the very last one, which later became "Bar Association". (Star Trek: Deep Space Nine Companion (p. 315))
One DS9 speculative script and multiple unused stories were devised by Christopher L. Bennett. He recollected, "My DS9 spec script actually got me a pitch invitation. I went out to L.A. and pitched to Robert Hewitt Wolfe; he didn't take any of my pitches, but his comments about them drove home the importance of focusing on character, a lesson that's been very helpful to me." (Voyages of Imagination, p. 146)
Three DS9 story ideas were conceived by Armin Shimerman, Eric A. Stillwell and David R. George III. Recalled Shimerman, "David George, partnered with Eric Stilwell, asked if I would join them to pitch episode ideas for Deep Space Nine. We worked for several months honing our plot points and eventually had our shot with writer/producer René Echevarria. Unfortunately, No sale." (Voyages of Imagination, p. 245)
Similarly, three story pitches were suggested by Gary Holland at a pitch session with Ira Steven Behr, Robert Hewitt Wolfe and Peter Allan Fields, toward the end of DS9 Season 2. Although one of these ended up as the genesis of DS9: "The Collaborator", the other two ideas were quickly dismissed by Behr, Fields and Wolfe. (Star Trek: Deep Space Nine Companion (p. 147))
In an initial pitch session for writing partners Bradley Thompson and David Weddle, they too proposed ideas to Ira Steven Behr. They specifically went "through this incredible list," said Thompson, "pitching one-liners and stories and stuff that just didn't fit the show's needs." (Star Trek: Deep Space Nine Companion (p. 437))
Multiple story pitches were likewise unsuccessfully submitted by Lisa Klink, who the producers called in to pitch. "I came back a second time," she stated, "and they basically realized I had ideas that were somewhere in the ballpark. They kept calling me back." (Cinefantastique, Vol. 28, No. 4/5, p. 101) Klink found it particularly easy to suggest story ideas during a subsequent six-week internship at Star Trek: Deep Space Nine, while it was in its third season. "I think, because I already knew them and had dealt with them in the pitches," she reckoned, "I could throw out ideas more easily in the story meetings and break sessions than some other interns might have." (The Official Star Trek: Voyager Magazine issue 6, p. 43)
One undeveloped character concept was that, in the third season episode "Second Skin", Robert Hewitt Wolfe – who wrote the installment – wanted to establish that Kira Nerys basically wasn't, in fact, Bajoran. "Originally," reported René Echevarria, "Robert wanted to say that Kira was Cardassian, that the arc of the show was that the real [Bajoran] Kira died, but she [Kira's Cardassian counterpart] is essentially Kira now and it doesn't really matter." Rick Berman and Michael Piller objected to this proposal. "I think Rick and Mike [...] thought that it was too weird, too alien a notion for the audience to really hold on to a character they had invested themselves in [....] They were probably right in that decision." Echevarria also observed that the abandoned concept was "very similar to when we wanted to kill Will Riker and keep" his transporter duplicate, Thomas Riker, in TNG: "Second Chances". (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 85)
Another scrapped character concept was that the DS9 writing staff initially planned for Odo, in the sixth season of the show, to intentionally become increasingly withdrawn from his crewmates, locking himself away and refusing to socialize with anyone else on the Deep Space 9 space station. This would have been motivated by feelings of guilt over the fact that he had assisted the Dominion in a six-episode story arc which begins that season. For the rest of the season, the character would have been written differently from ever before. Ronald D. Moore was starting to plan this story arc when Odo actor Rene Auberjonois alerted the writing staff that he had misgivings about it. Changing the character so drastically lacked a clear motive; the writers hadn't considered precisely what to do with Odo thereafter, and alienating him from the rest of the main characters without any reason even seemed wrong. That realization led the creative staff to agree with Auberjonois and ultimately abandon the notion. (Star Trek: Deep Space Nine Companion (p. 507))
Yet another discarded character concept was fallout of Dukat threatening Sisko, at the end of sixth season installment "Waltz", that he would "learn what it's like to lose a child." Sisko would then have had to become determined to protect his son, Jake, which Ron Moore expected would be "an awkward thing to have to work into every episode" and even "a pain." As a result, Dukat's threat to Sisko instead became declaring that he wouldn't be able to save Bajor's populace. (Star Trek: Deep Space Nine Companion (p. 522))
- 1 Undeveloped DS9 episodes and story concepts
- 1.1 Bashir-Dax love story
- 1.2 Cardassian O'Brien story
- 1.3 Circus story
- 1.4 Cirroc Lofton's Michael Jordan story
- 1.5 "Cold and Distant Stars"
- 1.6 Crossover with TNG
- 1.7 Day at Quark's
- 1.8 Dominion artificial wormhole
- 1.9 "Dysfunctional"
- 1.10 Eddington's escape
- 1.11 Evan Somers' pitch
- 1.12 Ferengi prejudice story
- 1.13 Garak and Tain story
- 1.14 "Giant"
- 1.15 The Guns of Navarone story
- 1.16 Iotian episode/"A Piece of the Action" sequel
- 1.17 Jennifer Sisko assimilation story
- 1.18 Klingon Hell
- 1.19 Lisa Klink's Dax script
- 1.20 Lisa Klink's imprisonment story
- 1.21 Murder mystery episode
- 1.22 Musical episode
- 1.23 Nausicaan episode
- 1.24 Nicholas Corea's starting point
- 1.25 "Persistence of Vision"
- 1.26 "Rapture" genesis
- 1.27 Ro Laren return
- 1.28 "Quorum"
- 1.29 Sito Jaxa return
- 1.30 Space locusts
- 1.31 Submarine episode
- 1.32 Thomas Riker return
- 1.33 A trio of love stories
- 2 Hypothetical season 8
Undeveloped DS9 episodes and story concepts
Bashir-Dax love story
Early in the run of Star Trek: Deep Space Nine, Michael McGreevey pitched a story to the DS9 writing staff that featured Jadzia and Bashir falling in love. McGreevey commented, "It was a love story, a simple concept. I don't know why they didn't want to do it. The symbiont inside Dax becomes ill, making her ill, and Dr. Bashir must separate them in order to treat the symbiont. We would come to see the personality of Jadzia, which of course is different from Dax. Bashir falls in love with her, and she feels for him, too. But the most important thing in life is to be joined with the symbiont. Bashir realizes that the only way to save the symbiont is to put it back into Jadzia, and thereby lose the girl he loves." (The Official Star Trek: Deep Space Nine Magazine issue 8)
Cardassian O'Brien story
A plot idea Robert Hewitt Wolfe thought up for DS9 focused on Miles O'Brien and stemmed from an undeveloped TNG story. "I kept thinking about a way to do that as a DS9 episode," he remembered, "and for a long time thought it would be cool if O'Brien was a Cardassian who had been replaced when serving on the Rutledge." (Cinefantastique, Vol. 27, No. 4/5, p. 95) In fact, Wolfe imagined O'Brien having been replaced during the Setlik III massacre. (Star Trek: Deep Space Nine Companion (p. 177)) This would have made O'Brien conceptually very similar to Raymond Boone, from DS9: "Tribunal". Wolfe explained, "The replacement [in O'Brien's case] was a deep-cover agent who'd been given O'Brien's memories [and didn't know he was Cardassian]." (Star Trek: Deep Space Nine Companion (p. 177)) A problem of logic faced Wolfe, though, as he couldn't understand why, if O'Brien was actually a Cardassian, his daughter, Molly O'Brien, looked Human. Wolfe rewrote the episode as "Second Skin", replacing Miles O'Brien with Kira Nerys. (Cinefantastique, Vol. 27, No. 4/5, p. 95)
A story inspired by magician Jeff McBride was devised for the series by Christopher Teague, with the intention of enabling McBride to appear in the episode. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 84) The plot concept was pitched to DS9 by Teague and bought from him. Ronald D. Moore later recalled that the story regarded a "circus coming to Deep Space 9, and this magician was in it." René Echevarria added, "It was an Odo show, about Odo's dreams, or a figure that he was chasing." (Star Trek: Deep Space Nine Companion (pp. 174-175)) This figure was a mysterious, masked man, inspired by masks used by McBride during his show. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 84) The idea of bringing a visiting circus onto DS9 didn't appeal to the writers. "We thought, 'Well, we're not gonna to do that,'" related Moore. (Star Trek: Deep Space Nine Companion (p. 175)) Nonetheless, the DS9 writing staff struggled with the story concept, eventually rewriting it as the episode "Equilibrium". (Cinefantastique, Vol. 27, No. 4/5, p. 95)
Cirroc Lofton's Michael Jordan story
Cirroc Lofton recalled to Star Trek: The Magazine Volume 2, Issue 5, p. 21, having pitched a completed script to Behr when he was about 18 years old, in which an argument between Captain Sisko and Jake resulted in Jake obsessing over basketball instead of baseball on the holodeck. Lofton suggested NBA legend Michael Jordan, having gone over to baseball at the time, could guest star as himself on the holodeck character and serve as a bridge between the two. Lofton noted the basketball story was the B-plot, and that the primary plot focused on Quark putting something addictive in his bar's drinks. Though everyone was nice and respectful, the idea was shot down for being too similar to TNG: "The Game" and the sentiment that: "Michael Jordan's not going to come here and do that!"
"Cold and Distant Stars"
A story imagined by Robert Hewitt Wolfe involved Benjamin Sisko waking up on a beach in 1995 Santa Monica, disheveled and disoriented. He was aware he was a Starfleet commander, though everyone around him believed he was mad. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 89) Related Wolfe, "I wanted Sisko to be saying, 'I'm the captain of a starbase in the year twenty-three-whatever, and I don't belong here.' And everybody's telling him, 'You're a homeless schizophrenic, take your Thorazine.'" Wolfe wrote the concept into a script called "Cold and Distant Stars". The title related to Sisko, as a homeless man, looking up at the sky in the knowledge that was where he belonged.
There were problems with the story. "That never quite worked," Robert Wolfe admitted. (Star Trek: Deep Space Nine Companion (p. 196)) He further critiqued, "The problem with my concept is that Brannon [Braga] went and did it with Riker in an insane asylum [in TNG's "Frame of Mind"]." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 89) Ira Steven Behr agreed, "It just didn't work for me." (Star Trek: Deep Space Nine Companion (p. 196)) However, Wolfe managed to sell Behr the idea – which Wolfe later referred to as "snake oil" – in DS9 Season 2. Reflected Wolfe, "I sold him the idea that Sisko would wake up on Santa Monica beach. He would say, 'I am a starship captain,' and the locals would say, 'Yeah, right.'" (Cinefantastique, Vol. 27, No. 4/5, p. 92) The story was rewritten as third season two-parter "Past Tense, Part I" and "Past Tense, Part II". (Star Trek: Deep Space Nine Companion (p. 196); Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 89; Cinefantastique, Vol. 27, No. 4/5, p. 92) A Starfleet Captain is found homeless, formerly institutionalized, and on the Los Angeles area pier by the crew of Voyager in "Future's End".
Another unused idea which also served as the basis for that two-parter was crafted by the writers because they wanted to avoid using time travel. "I had an idea where Sisko's consciousness gets disconnected from his body," stated Robert Wolfe, "and hooked into the mind of an ancestor with a similar genetic makeup, like two radios tuned to the same frequency. The idea came from the fact that my wife has been a counselor for the mentally ill homeless for a long time, and I've learned that just because they say they are something they couldn't be, doesn't mean it's not true for them." René Echevarria added, "Part of Robert's idea was that Sisko would see a cop and it would be Rene Auberjonois without his makeup. The homeless counselor would be Dax without the spots. Sisko would be seeing these blurry things and realize he was seeing through some weird filter. Robert wrote different drafts of the story with different tech." (Cinefantastique, Vol. 27, No. 4/5, p. 92)
Crossover with TNG
A crossover between Deep Space Nine and Star Trek: The Next Generation was originally considered as one way to conclude DS9's first season. In the story, the two crews would have opposed an intergalactic invasion force. The plot was vetoed by Rick Berman. (Cinefantastique, Vol. 24, Nos. 3/4, p. 108) Commented Ira Steven Behr, "[It] had to do with the Cardassians deciding they wanted DS9 back, and we looked at it and what it would cost to do it right. It would have required a lot of money." The first season instead ended with the standalone installment "In the Hands of the Prophets", and the envisioned two-parter, though never produced, went on to serve as the template for the second season finale, "The Jem'Hadar". (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, pp. 36 & 37) The notion of the Cardassians wanting to retake DS9 was featured in the fifth season ender, "Call to Arms", and a subsequent six-part story arc at the start of the sixth season.
Day at Quark's
Dominion artificial wormhole
According to Star Trek author John Vornholt, a storyline was in development "about the Dominion building an artificial wormhole, which had to be destroyed by a dangerous commando raid". However, this story was dropped after Vornholt had his The Dominion War duology, Behind Enemy Lines and Tunnel Through the Stars, approved by Paramount, something which Vornholt regretted, considering there was room for both stories. (Voyages of Imagination, p. 440)
"Dysfunctional" was an episode which was planned for DS9 Season 7. In that story, Ezri Dax secretly arranged to have the Dax symbiont removed by an alien doctor, because she felt she could no longer cope with her new lifestyle. (SFX: The Essential Guide to Deep Space Nine, p. 98)
Since the end of Season 4 until the beginning of development on fifth season two-parter "In Purgatory's Shadow" and "By Inferno's Light", the DS9 writing staff discussed doing a version of The Great Escape, a film favorite of theirs, on the space station. For a long while, they had considered portraying the episode from Michael Eddington's perspective, "with him in the brig and showing how he breaks out, forcing the audience to kind of root for the guy," explained Ira Steven Behr. "It never worked out, because we weren't confident that the fans were really behind the character." Although this story concept was abandoned, the idea of a prison break, inspired by The Great Escape, influenced the development of the aforementioned two-parter. (Star Trek: Deep Space Nine Companion (p. 422))
Evan Somers' pitch
During the first season, Evan Carlos Somers pitched a story idea for the series. "It was originally supposed to be just Robert [Wolfe] in my pitch meeting," he stated. "Ira [Steven Behr] was supposed to run off to some meeting, but at the last minute, he said, 'Well, it's Evan, the trainee; we owe him this.' He had somebody waiting, [but] he held him in abeyance and took my pitch. I got very close, and there was one dissenting voice. I understood why he didn't think it would work and I left feeling there was a chance, maybe I would come back to pitch. I asked Ira if he could steer me in a more precise direction, and he loaded me down with the most recent final drafts of all the episodes he had. He said they wanted more character-driven than plot-driven material, and that I tended toward the plot-driven." Despite his pitch having been rejected, one week later, Somers was brought in to work on the writing of the episode "Battle Lines", after which he joined the series' writing staff. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, pp. 31-32)
Ferengi prejudice story
One of the three story ideas submitted by Armin Shimerman, Eric A. Stillwell and David R. George III dealt with prejudice and Ferengi. Referring to this plot concept, Shimerman noted, "Of the three pitch ideas, I gravitated to the one that was most interesting and upsetting." (Voyages of Imagination, p. 245) He elaborated, "The episode would have focused around inherent racial prejudice, not just for Ferengis but for other entities [and/or species] as well [...] I just wanted to explore that theme." (Cinefantastique, Vol. 32, Nos. 4/5, p. 35) At Shimerman's suggestion, he and George turned the pitched story into the novel The 34th Rule. (Voyages of Imagination, p. 245)
Garak and Tain story
A story involving the characters of Elim Garak and Enabran Tain was conceived and pitched by Judy Klass, a freelance writer, from whom the DS9 writing staffers bought the premise. The story established Garak as the son of Enabran Tain. "We were never able to do the full-blown show about that," recalled Robert Hewitt Wolfe. Despite the story's omission, the detail of Garak being Tain's son was worked into the series. (Cinefantastique (Vol. 29, No. 6/7, p. 38)
Steven DeKnight submitted a script which would have revealed that Ferengi were originally large and savage, but evolved to be smaller and sneakier. It would have featured a Ferengi scientist who had genetically modified himself to be like the giant Ferengi of old.
"I wanted to do something that was fun and a little bit different. The spec was called "Giant." It starts out in Quark’s bar and Worf is there with Jadzia Dax. He goes up to the bar to get a drink and he comes back to the table to discover there’s a Ferengi hitting on his girlfriend. He tells the Ferengi to get lost and the Ferengi gets feisty. Worf says, I remember this line, “There’s no honor in fighting a single Ferengi.” And he hears a voice behind him saying, “I’d say the same thing about Klingons.” And he turns around and there’s a giant Ferengi behind him that’s bigger than he is. So that’s the start of it and when we come back it’s your classic bar fight with Worf and this giant Ferengi, who goes toe-to-toe with Worf. And from there, everybody gets thrown into the brig."
"You find out as the story unfolds that these two Ferengis are brothers, the regular Ferengi and the giant Ferengi. The big one is a scientist and he discovered there’s a secret the Ferengi have been hiding for like a thousand years: The Ferengi used to be big, they used to be like Klingons. And slowly they evolved, they got smaller, and basically sneakier, as an evolutionary survival tactic. Because, as you find out in the story, people underestimate you when you’re small. They don’t consider you a threat. And that’s how you can screw them over. So the scientist discovered that there’s a genetic modification he can make to restore Ferengi to their rightful place. And he has this dream of Ferengis becoming large again and being respected."
"The story from there basically goes that Worf and Dax have to transport these two guys, because they’re wanted fugitives from the Ferengi empire, and hand them over. And on their way transporting them, they get attacked by a Jem'Hadar ship. From there it becomes this adventure, as they crash land on this planet, of Worf and Dax having to work together with these two Ferengi to get off the planet and escape the Jem’Hadar. And at the end of the episode, Worf has gained a lot of respect for this giant Ferengi. And he lets him go. He helps him escape." (8 Star Trek Spec Scripts That Never Saw the Light of Day at Vulture.com)
An episode inspired by the film The Guns of Navarone was temporarily to have been written by Michael Taylor. "The producers brought me out to California to write a military adventure that was sort of based on The Guns of Navarone," he laughed. "But after I got here, that concept didn't seem to be interesting to anyone." Taylor went on to write the sixth season episode "Resurrection". (Star Trek: Deep Space Nine Companion (p. 509))
Iotian episode/"A Piece of the Action" sequel
Before Ronald D. Moore joined the writing staff of Star Trek: Deep Space Nine, he devised and pitched a story featuring Iotians and their homeworld of Sigma Iotia II, that planet and its people having been introduced in TOS: "A Piece of the Action". In Moore's story, the Iotians had essentially become impersonators of James T. Kirk and Spock, whom they meet in that earlier installment. (The Fifty-Year Mission: The Next 25 Years, p. 510)
When DS9 was scheduled to mark Star Trek's thirtieth anniversary with a special commemorative episode, Moore got an opportunity to again pitch this idea. It was the first concept which the writing staff considered for the thirtieth-anniversary milestone show. Moore imagined Captain Sisko and his DS9 crew returning to Sigma Iotia II after approximately a hundred years since the time of "A Piece of the Action". The newcomers would find that the fanatical Iotians had based a whole religion on the Federation. (Cinefantastique, Vol. 29, No. 6/7, p. 64) Moore noted, "They have conventions, they know all the adventures." (The Fifty-Year Mission: The Next 25 Years, p. 510)
The concept would have allowed for commentary on Star Trek in general, with the Iotians representing the franchise's fans. (The Fifty-Year Mission: The Next 25 Years, p. 510) "To me, it was to send the [DS9] characters to a Star Trek convention, which I thought would be fun, and a kind of comment on fandom, and people's involvement with the show from afar," Moore remarked. (Cinefantastique, Vol. 29, No. 6/7, p. 64) He thought the notion was "kind of a cool idea" and would make for an "interesting" episode. (Cinefantastique, Vol. 29, No. 6/7, p. 64; The Fifty-Year Mission: The Next 25 Years, pp. 510-511)
However, there were some problems with the story. Co-Supervising Producer Hans Beimler remembered, "We really weren't comfortable with it, although we were having a lot of fun. There was something that was bothering all of us, but especially Ira [Steven Behr], which was that in a way we were making fun of the people who watch and are our fans. That didn't feel right to Ira, to sort of poke too much fun at them. After all, they are the fans, they are what makes the show work. We owe our livelihood to them. So it wasn't quite sitting well." (Cinefantastique, Vol. 29, No. 6/7, pp. 64-65) Ron Moore added, "René Echevarria thought it was a dangerous show to do; that we would be talking down to the fans on some level and perhaps it wasn't the best way to go." (The Fifty-Year Mission: The Next 25 Years, p. 511)
Star Trek's thirtieth anniversary was ultimately celebrated with the episode "Trials and Tribble-ations". Ron Moore's original idea for the episode was later picked up by Star Trek: Voyager, in the episode "Virtuoso". However, since that entry was set in the Delta Quadrant, contact with the Iotians was a physical impossibility. Instead, the crew of the USS Voyager stumble upon a technologically advanced culture which lacks the concept of music; fascinated by The Doctor's singing, the aliens begin to idolize him.
Jennifer Sisko assimilation story
Ronald D. Moore's original concept for DS9: "Soldiers of the Empire" was for Worf and the crew of the Rotarran to enter Gre'thor. (Star Trek: Deep Space Nine Companion (p. ?)) While ultimately unused in DS9, this concept was later developed into VOY: "Barge of the Dead". (AOL chat, 1999)
Shortly after Lisa Klink mistakenly submitted a TNG speculative script mere weeks before TNG was cancelled, she wrote a spec script for Star Trek: Deep Space Nine. Its premise was about the theft of the Dax symbiont. However, disappointment ensued when Klink discovered that this idea had already been thought up and that the resultant episode, "Invasive Procedures", was to air on the exact same day as she mailed her DS9 spec script. "I just tore my hair out," she laughed. "I couldn't believe it, because you can only submit two spec scripts without an agent, and those were my two! I figured I had just used up all my chances." (The Official Star Trek: Voyager Magazine issue 6, p. 41)
Originally, Lisa Klink thought up a story that dealt with imprisonment. "The original idea was initially Bashir getting thrown into an alien prison," Klink noted. (Cinefantastique, Vol. 28, No. 4/5, p. 30) Explained René Echevarria, "It was a planet where we end up in this camp; we think these are the people who live here, but it turns out that they are not native to this planet and that they are fighting the natives off. We realize we are on the wrong side and that we have been helping fight off some kind of aliens living in the forest, when in fact they are the natives who are fighting a war of rebellion." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 106) At the behest of the DS9 writing staff, the rest of this plot was abandoned, retaining only the idea of Bashir being imprisoned by aliens. Merged with a story by Nicholas Corea, the narrative ended up becoming a precursor of the fourth season episode "Hippocratic Oath", with the aliens changed to be Jem'Hadar. (Cinefantastique, Vol. 28, No. 4/5, p. 30; Star Trek: Deep Space Nine Companion (p. 266))
Murder mystery episode
Michael Jan Friedman commented on a story he pitched: "While DS9 was still on the air I pitched a story to Ron Moore. It was a murder mystery-type thing involving Kira. Ron said he liked the idea, but it was a little too close to an episode they were already working on. That episode was "The Darkness and the Light"." (Voyages of Imagination)
Ronald D. Moore advocated doing a musical episode. "Oh, and I was agitating for a musical, man," he stated. "On record, I wanted to do a musical version of Trek well before Buffy or Chicago Hope. I wanted to do a musical episode, and nobody would f***in' do it." When the interview spoke of how this was accomplished on Buffy the Vampire Slayer, Moore responded, "Yeah, that's all we needed to do. There's just some tech virus that infects the crew and they can only communicate in song, you know? And just do it! And have a ball."  Moore had encountered similar opposition to doing a musical episode in TNG. (All Good Things (Blu-ray) audio commentary)
In 1997, Ira Steven Behr commented to Star Trek Monthly, "You know the Nausicaans? They'll be back, and we'll do a show about them being an enemy for an episode." ("On Things Past, Present and Future", Star Trek Monthly issue 30, p. 10)
Nicholas Corea's starting point
The story which Nicholas Corea devised and which was later combined with a story from Lisa Klink, to become "Hippocratic Oath", was based around a group of Jem'Hadar who were trying to free themselves from their addiction to ketracel-white. (Star Trek: Deep Space Nine Companion (p. 266)) This was the first time the name was used, as it had previously been described as a "missing enzyme" in "The Abandoned" and simply as a drug to which the Jem'Hadar were addicted in "The Die is Cast".
"Persistence of Vision"
A story written by Robert Hewitt Wolfe for DS9 Season 2 was inspired by him and Ira Steven Behr having a discussion about virtual reality, Behr asking, "How scary is it going to be in the future when you won't be able to tell what's real and what isn't?" Wolfe's subsequent story had Miles O'Brien and Jadzia Dax entering a virtual reality prison. The pair seemed to escape but then realized they were still in the prison. "Then they escape again," Wolfe related, "and I wanted the tag to be where Keiko was telling O'Brien how good it was for him to be back, and O'Brien saying, 'I don't know whether I'm back or not. I'm never gonna know.' Fade out."
Michael Piller forced Robert Hewitt Wolfe into discarding the story, instead writing the similar Season 2 episode "Shadowplay". Although both stories featured the character of Rurigan, "Persistence of Vision" focused more on him and was considerably more downbeat. Some of the plot was reused in third season opening two-parter "The Search, Part I" and "The Search, Part II". (Star Trek: Deep Space Nine Companion (pp. 122-123)) Additionally, the title "Persistence of Vision" was reused for "Persistence of Vision" of Star Trek: Voyager.
A story pitch by L.J. Strom provided the basis for the script of "Rapture". However, Hans Beimler once remarked that the original story was completely different to how it turned out. (Star Trek: Deep Space Nine Companion (p. 405))
Ro Laren return
The writing staff of Star Trek: Deep Space Nine briefly considered and discussed creating an episode which would have featured Ro Laren, who had defected to the Maquis in TNG: "Preemptive Strike". This undeveloped DS9 plot would have featured her in the Maquis. "The story never worked out," noted Ira Steven Behr. As a result, the group of writers instead wrote about Thomas Riker, newly defected to the Maquis, in the third season episode "Defiant". (Cinefantastique, Vol. 27, No. 4/5, p. 98)
Jack Treviño and Toni Marberry sold three stories to Deep Space Nine, but only two were filmed. The third story, sold about a year after the team sold "Little Green Men" and "Indiscretion", was called "Quorum". However, it went unproduced. 
Sito Jaxa return
One story considered by the writing staff concerned the return of Sito Jaxa from TNG: "Lower Decks". The pitch had Sito being imprisoned under inhumane conditions and suffering from post-traumatic stress disorder. Robert Hewitt Wolfe developed the story for some time. Feeling that there was insufficient explanation of Sito's condition, he had Sito killing her cellmate, whom she'd become close to. (Star Trek: Deep Space Nine Companion (p. 326)) According to Ronald D. Moore, "We talked about this for quite awhile, but then decided that bringing Sito back would rob 'Lower Decks' of a great ending." (AOL chat, 1997)
While unused, Wolfe later incorporated elements of the story into "Hard Time". He commented, "I took the end of the Sito story and threw away the rest." (Star Trek: Deep Space Nine Companion (p. 326))
A story that never made it in the script stage would have a swarm of space locusts heading for Bajor, the Bajorans unwilling to defend themselves because prophecy foretold the event. The staff never found a way to make the locust angle non-goofy, but locusts were eventually included in "Rapture" as a sort of in-joke. (Star Trek: Deep Space Nine Companion (p. 406))
Originally, the fourth season episode "Starship Down" was conceived with the Defiant sinking in an alien sea. However, the episode's setting was thereafter changed to the atmosphere of a gas giant. In hindsight, Ira Steven Behr remarked, "We were trying to do a submarine movie and if we want to, we can try again sometime." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 109) Although the writing staff tried to make some scenes in the Season 5 episode "For the Uniform" as if they were from a submarine movie, Behr noted that, for the rest of the series since "Starship Down", doing an entire installment based on that genre of film was an ongoing joke. "We'd say, 'You know, we could still do that submarine movie, and we could do it right this time!'" he recalled. (Star Trek: Deep Space Nine Companion (pp. 284 & 420))
Thomas Riker return
After "Defiant", Jonathan Frakes lobbied the producers to bring back Thomas Riker for a sequel episode. Frakes noted, "I keep thinking Tom is coming back [....] Don't you think it makes sense for them to send Kira over there to free Thomas? It's a no-brainer." Frakes, however, received no definite indication from the producers. (Star Trek: Deep Space Nine Companion (p. 191))
The Star Trek: Deep Space Nine Companion (pp. 191-192) states that, in the fourth season pitch letter sent to freelance writers, Thomas Riker was listed as a subject that the producers were not interested in hearing about. However, the authors note that this could have meant that the producers were already working on such a story. Several comments from Ronald D. Moore indicate that the writers indeed seriously considered the possibility. In a 1996 edition of Cinefantastique magazine (Vol. 27, No. 4/5, p. 98), Moore remarked, "We might see him again. We haven't really discussed the story, but we have talked about rescuing him someday." Similarly, in the 1996 book Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages (p. 87), Moore commented, "We'll probably see a return-of-Tom Riker episode. What's nice is he's not really a part of Next Generation, so he's ours, and we can do what we want with him and not worry about what the movies do with Will Riker." Likewise, in an online chat with fans, Moore noted, "Tom Riker may or may not get rescued at some point." (AOL chat, 1997)
In an interview with Jonathan Frakes provided in the TNG Season 6 DVD box set, he stated that he had approached Moore regarding a Thomas Riker episode involving Damar's rebellion. However, the character never appeared again.
A trio of love stories
During early development of the fourth season episode "The Muse", a never-developed series of romantic subplots was thought up, which would have been somewhat similar to the third season installment "Fascination". The multitude of B-stories was conceived after Majel Barrett-Roddenberry suggested an A-story, with her character of Lwaxana Troi returning to the space station, pregnant, and claiming that the father of her unborn baby was Odo. "That started us thinking about a set of stories about love on the station, and about different aspects of desire," remembered Ira Steven Behr. René Echevarria added, "We decided to do a very soft show about different romances: Rom and Leeta, Sisko and Kasidy, O'Brien and Keiko. And the fourth romance would be Odo and Mrs. Troi." (Star Trek: Deep Space Nine Companion (pp. 335 & 336)) In another interview, Echevarria conversely stated that one of the romantic plot threads was to have been "Bashir and O'Brien and Keiko and Leeta, some kind of weird double date, Bashir having an infatuation with Leeta... or something like that." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 118) In yet another interview, he recalled that the trio of subplots had been "all small, keeping the different romantic things we had going. We had something with O'Brien and Keiko, with Shakarr [sic] and Kira, with Odo and Lwaxana, and with Bashir and Lita [sic]." Regardless of which four romances would have been focused on, Echevarria continued, "I wrote a couple drafts of the story [about those romances] and we decided it was too flimsy and too soapy." (Cinefantastique, Vol. 28, No. 4/5, p. 60) He elaborated, "It just didn't gel. Nobody was very excited. We decided that the plan was a little too soft." (Star Trek: Deep Space Nine Companion (p. 336)) Eventually, the A-story became the B-story of the episode "The Muse", which scrapped the three additional romances, instead focusing on not only the connection between Odo and Lwaxana Troi but also on Jake Sisko's relationship with an alien muse named Onaya. (Star Trek: Deep Space Nine Companion (p. 336))
Hypothetical season 8
As Star Trek: Deep Space Nine ends with its seventh season, no other episodes were ever developed or produced with the serious intention of subsequently being included in the series. However, in 1999, Nana Visitor postulated a continuation of DS9, commenting, "I think, maybe foolishly, but I think we could have gone on. I think there were more stories to tell [….] I think it could go on from the way the last episode is. I think you could start again the next year, with what's happening now, but it's got to end sometime." ("Crew Dossier: Kira Nerys", DS9 Season 1 DVD special features)
For the documentary What We Left Behind, the show's writers reassembled on 8 March 2015 to break the story for a hypothetical new episode. This was only written for the purposes of the documentary, rather than actually being intended for production, even though the writing team wrote it as a hypothetical Season 8 premiere that could theoretically be produced. (For more information, see the article What We Left Behind.)