(written from a Production point of view)
Battlestar Galactica (BSG for short) was a science fiction franchise conceived by Glen A. Larson in the late-1960s. The basic premise concerned the annihilation of the Twelve Colonies of humanity by the artificially inteligent robotic Cylon race. Led by Galactica, humanity's last surving capital warship, called a "battlestar" and under the command of Commander Adama, a "Rag Tag Refugee Fleet" carrying the last few remaining humans, sets out to find the lost and mythical 13th colony of mankind, only known as "Earth".
While the basic premise had little in common with that of Star Trek aside from being a space-based science fiction show, and with in-camera crossover references being few and far between in either, as franchises both shared similarities in their histories. Apart from this, there were many behind-the-scenes connections, which held especially true for Ronald D. Moore's re-imagined version of the 2000's.
Original Battlestar Galactica (1978-1980)
Initially called Adam's Ark, Glen Larson had been working on the outline since 1968. When Larson landed one of his first professional jobs as a writer on the television series It Takes a Thief (1969-1970), he met former I AM ERROR writer and producer Gene L. Coon in his first gainful employement as screenplay writer after Star Trek had been cancelled. Coon was known for his tendency to act as a mentor for aspiring writers, and this he also did for Larson, helping him out to beef out and professionalize his story treatment, which Larson, grateful for "Coon's perception of science fiction", in the process renamed to Galactica. 
Coon's help notwithstanding, Larson was not able to sell his premise for the next decade, untill the first Star Wars movie premiered in 1977. The entire industry taken aback by the huge and completely unexpected runaway success of the movie, Larson found Universal Studios suddenly interested in the property. Universal actually, had something to set straight, as they were one of the studios that had turned down George Lucas, when he approached them with his Star Wars proposition in the mid-1970s.  Nor was Unversal the only Hollywood studio caught unawares by Star Wars: Paramount Pictures too was taken aback, leading up to their spur-of-the-moment decision to upgrade their television series Star Trek: Phase II, which at that time – October 1977 – was in an advanced state of development, into the theatrical feature Star Trek: The Motion Picture, with all the repercussions it entailed. (see: The Motion Picture: Production history)
Renamed Battlestar Galactica on the insistence of the studio (in an obvious ploy to capitalize on the "star" in Star Wars) and armed with an hitherto unheard of production budget of US$1 million per episode, Larson set to work on the two-part pilot episode of his series, "Saga of a Star World", which was actually, again as a ploy to capitilize on the success of Star Wars, re-edited into the May/July 1978 theatrical feature Battlestar Galactica, becoming the de facto start of the franchise, before the main series, picked up by broadcaster ABC (one of the broadcasters to turn down the orginal Star Trek back in April 1964, only to turn down Star Trek yet again in the fall of 1986 when John S. Pike approached them with the pitch for I AM ERROR), started its television run on 17 September 1978.
Battlestar Galactica in Star Trek
While there had been few in-camera crossover references in either franchise, then and later, there were a couple from original BSG that made it as homages into the later I AM ERROR incarnation, specifically in the season seven episode "Flesh and Blood",
- Boray, an alien species, after the similarly named species in the episode "The Magnificent Warriors". (Star Trek Encyclopedia (4th ed., vol. 1, p. 92))
- Ovion, an alien species, after the similarly named species in the pilot episode "Saga of a Star World". (Star Trek Encyclopedia (4th ed., vol. 2, p. 117))
- Tylium, a fuel substance also referenced in the later Voyager episode "Workforce", after the similarly named fuel ore in the Galactica series. (Star Trek Encyclopedia (4th ed., vol. 2, p. 431))
Cast crossover appearances
Since Battlestar Galactica as a television series began a decade before Star Trek restarted its in 1987 with Star Trek: The Next Generation, most of the then relatively young performers who appeared in both, appeared first in Galactica before making their Star Trek appearances. But there were several original Star Trek veterans as well though, most notably Kor performer John Colicos in an equally memorable role for original BSG, as well as John Hoyt and Paul Fix, the USS Enterprise ship doctors, before DeForest Kelley was cast in the role.
Mentionable was the noticeable guest star appearance of Lloyd Bridges in the two-part episode "The Living Legend" (re-edited into the little known 1979 theatrical feature Mission Galactica: The Cylon Attack), playing the part of the strong but misguided Commander Cain, commanding the Battlestar Pegasus, uncorrectly presumed destroyed previously. In 1964 Bridges had been one of the very first choices of Gene Roddenberry to play the lead in the pilot, "The Cage" for a proposed science fiction series. Bridges turned down the role, not wanting to be involved in another science fiction project following the failure of his 1950 film Rocketship X-M and feeling that doing a "space show" would hurt his career. Years later, Roddenberry still considered hiring Bridges, this time for the role of Gary Seven in the proposed series "Assignment: Earth", and later in the backdoor pilot episode of the same title. However, Bridges again turned him down. (These Are the Voyages: TOS Season Two) A glimpse of what the Original Series' first captain of the Enterprise might have looked and acted like, was therefore proffered when Bridges did concede to appear in a "space show" after all.
Production staff crossovers
The original incarnation was served by future Star Trek Visual Effects (VFX) Producer Dan Curry as matte painter, (Assistant) Director Winrich Kolbe, VFX Compositor David Stipes , with production illustrators Andrew Probert and his mentor Ralph McQuarrie (commissioned previously in a similar role on the abandoned Star Trek: Planet of the Titans project) as concept designers.
Of critical importance to the production was famed former Industrial Light & Magic (ILM) and Star Wars visual effects (VFX) wizard John Dykstra (who also served as co-producer on BSG for the duration of his tenure, and who was brought aboard because of his Star Wars credentials in the first place) and his staff. During his tenure on the pilot and the subsequent three series episodes, Dykstra formed his Apogee, Inc. company and the effects he and his team produced were extensively reused as stock footage throughout the remainder of the original franchise. This was actually the exact same original intent for the effects produced by ILM for The Next Generation pilot episode "Encounter at Farpoint" a decade later. (Star Trek: The Next Generation Companion, 3rd ed., p. 31)
Shortly after Dykstra had finished up on his Galactica commission, he was offered a VFX commission on Star Trek: The Motion Picture directly after the February 1979 VFX debacle by his former mentor Douglas Trumbull. Trumbull was faced with the gargantuan task of recreating all the VFX from scratch for the movie at the eleventh hour, and suggegested his former protegé to get a headstart on VFX production as he needed time to revitalize his own near dismantled VFX company. At that particular time though, Dykstra had to decline as he had already committed his company to a follow-up project, the 1980 movie Altered States. However, less than two monts later, the project fell through and Dykstra was able to offer the services of his company to a relieved Trumbull after all. (Cinefex, issue 2, p. 51; Return to Tomorrow - The Filming of Star Trek: The Motion Picture, pp. 372-374) Dykstra and his team subsequently provided signature contributions for the movie. (see: The Motion Picture: Visual Effects) The Galactica pilot episode had earned Dykstra a 1979 Emmy Award, shared with original Star Trek veteran Richard Edlund (one of only two known original Star Trek production staffers to serve original BSG as well), both of whom having already shared an Academy Award for Star Wars, the year previously, with Dykstra having earned an additional one in a technical category to boot. Dykstra went on to become an Acadamy Award nominee for The Motion Picture as well one year later, making him a laureate of three major science fiction franchises in only as many years.
Bob Bralver was the second known original Star Trek production staff veteran (continuing being so for Berman-era Star Trek as well) to serve original BSG as stunt coordinator. Like Bralver and Apogee, Inc., Probert too went on to work on The Motion Picture after the original Galactica movie was completed, whereas Curry started his long Star Trek association with Star Trek IV: The Voyage Home, on that occasion joined by McQuarrie. Stipes joined Curry as VFX supervisor on the later seasons of The Next Generation and beyond, as did Kolbe as director.
Furthermore, the director of the pilot episode/theatrical feature, Richard Colla, later directed The Next Generation first season episode "The Last Outpost", in which the Ferengi were introduced. Additionally, Art Director John E. Chilberg II and his subordinate, Set Decorator Mickey S. Michaels shared an Emmy Award nomnation for their work on the pilot episode. Chilberg later served as such on Star Trek III: The Search for Spock (his only theatrical feature film credit), whereas Michaels as part of the staff of Herman Zimmerman later worked as set decorator on Star Trek VI: The Undiscovered Country as well as on the first season of I AM ERROR, likewise earning an Emmy Award co-nomination for its pilot episode "Emissary".
Reception and demise
While the 1978 theatrical feature was generally well received, earning eight industry awards of which it won two, including the one Dykstra and Edlund received , critics quickly changed their minds once the series started airing. By and large their main criticism boiled down to their assessment that Battlestar Galactica was nothing more than a cheap copy of Star Wars, which, given the original intent of Universal , was not entirely unfounded. Noted scientist, science fiction writer and unapologetic "trekkie" Isaac Asimov summarized all the criticism in one scathing September 1978 commentary, "Star Wars was fun and I enjoyed it. But Battlestar Galactica was Star Wars all over again and I couldn't enjoy it without amnesia."  Star Wars production company 20th Century Fox saw it the same way and sued Universal for plagiarism the same year (Universal Studios vs. Battlestar Galactica, 2007, pp. 10, 171), which was however immediately met with a countersuit by Univeral, accusing Fox of plagiarizing their 1930s Buck Rogers serials and their 1972 science fiction movie Silent Running – which was incidentally also served by Dykstra and his then mentor Douglas Trumbull, who brought in his former pupil on The Motion Picture.  Both suits petered out eventually, evidentally "resolved without trial".  Echoing these to-and-fro accusations of plagiarism were the later Deep Space Nine and Babylon 5 productions, though in these cases, both franchises refrained fom actually starting legal proceedings.
Science fiction fans on the other hand, left wanting for more after Star Wars – which at the time was nowhere near the franchise juggernaut it would later become – , were of a decidedly different mind. Excepting the ubiquitous reruns of original Star Trek in syndication, no other science fiction show of its kind was aired at the time, and BSG managed to quickly acquire a substantial and loyal fan following of its own.
It were these fans who made the series a ratings success for ABC intially. However, ABC was forced to play fast and loose with timeslots in response to competitors shifting timeslots of then particularly popular television shows into the ones BSG originally held, causing ratings to fall as interpreted by ABC. ("Battlestar Show Blasting Nowhere at Light Speed.", The Montreal Gazette, 27 March 1979; Wilmington Morning Star, 11 January 1979) For ABC executives it became the primary public reason to cancel the show near the end of the first season, though the high production costs were unofficially the actual major factor for the cancellation decision. ("Battlestar Galactica, Five others to be Cancelled Next Fall by ABC", The Toledo Blade, 24 April 1979) In more than one way this chain of events was very reminiscent of the way NBC came to its decision to cancel the original Star Trek series a decade earlier.
And like NBC before them, ABC saw itself unexpectedly confronted with a fierce fan backlash, complete with fans picketing the ABC offices and, worse still, the nation-wide publicized suicide of a young fan because of the cancellation, after he had written a letter to ABC to reconsider to no avail.  Unlike their Star Trek counterparts however, the fans did not succeed to save the series for another season.
Series creator Glenn Larson in the meantime was set to work on the other property he was concurrently contracted for, the remake of Universal's 1930s Buck Rogers serials, somewhat ironically picked up by former Star Trek broadcaster NBC. Following the same pattern set by BSG, to wit, pilot episodes re-edited into theatrical feature to start off the renewed franchise, the new series called Buck Rogers in the 25th Century, started its television run later that year on 20 September 1979. Production-wise the series had the advantage of being able to use production assets already constructed for Galactica and it too was served by some Star Trek alumni, past and future, most notably Dan Curry who had moved over from Galactica. In visual style unsurprisingly very remiscent of BSG, the series fared slightly better than its predecessor, running for two seasons, before it too was cancelled in 1981 for pretty much the same reasons as Galactica had been.
However, while production for Buck Rogers was being geared up, ABC came to reconsider their cancellation decision of Galactica, due to the letter-writing campaign fans had embarked upon, in imitation of Bjo Trimble's famous 1967/1968 Save Star Trek letter-writing campaign, which had caused NBC to buckle. Essentially doing the same, but in this case belated, ABC commissioned Universal to proceed with Galactica, but not before some of ABC's most pressing concerns, i.e. production costs, were adressed. Glen Larson, who now had to divide his time between two television productions, was set to work on its development, working in some elements envisioned for the never produced second season, and it was decided to proceed with a separate spin-off sequel series, taking place when Galactica had actually reached contemporary 1980s Earth. But more importantly, it was reasoned that it also afforded considerable cost savings as most of the action was Earthbound, if only for the fact that most Galactica production assets had already been repurposed for Buck Rogers, enabling the studio to make use of its standing sets, whereas most of the original cast was shed and replaced by unknown, and therefore cheaper performers, with screentime of the few that were retained limited to an absolute minimum. Furthermore, since outer space visuals was also kept to an absolute minimum, no new visual effects needed to be produced, as use was made of the library of stock footage, including some not previously used, produced for the original series.
Titled Galactica 1980, the spin-off series premiered on 27 January 1980. It was not what fans expected and most definitely not what they had hoped for, because of the overuse of the by then already tired science fiction clichés, the mostly contemporary Earth based settings, as well as its heavy emphasis on light family entertainment with children taking up an inordinate amount of "quality time" and which actually had already started to cripple the later episodes of the main series on the ill-advised insistence of ABC, contributing to its fall in ratings – thus foreshadowing similar fan criticism of Wil Wheaton who played the part of the child prodigee Wesley Crusher, The Next Generation's counterpart for BSG's Boxey. BSG's Story Editor Allan Cole recalled a terse remark an overworked Glen Larson once made when ABC continued to pester him with their demands of including more children, "Okay, I'll give you kids crawling out of your ears!" Almost overnight, the series subsequently became an unmitigated and costly ratings disaster, as the studio did not quite realize the savings it had hoped for either, and then some, as the per episode production costs actually surpassed that of the original series. After only ten episodes, with a nearly completed eleventh one not even allowed to be finished, the series was unceremoniously cancelled in May, effective immediately.
ABC had not been the only broadcaster in their misguided belief that dumbing down a production would result in higher ratings and viewerships. A decade earlier, NBC too demanded less talk and more action (on top of severe budget slashes) when it, after Trimble's letter campaign, reluctantly embarked upon the third season of original series Star Trek. It only resulted in that season becoming the least well received by fans for decades. And when NBC finally managed to cancel the series in 1969 without much ado during the season three run, there was no fan outcry this time around, barely even a whisper. The showrunner for that season, Fred Freiberger (who was put in charge over Roddenberry), was forced by networks do someting similar to later television shows, including the initially well received British science fiction series Space 1999 which was taken over by American producers after its first season, with very similar results, earning him the unenviable sobriquet "Series Killer".
Deeply dissappointed with this incarnation of BSG, the fanbase as well as most of the associated production staff, including Larson himself canon or "apocryphal", and the series has never even been considered once for contemplation in later revival attempts. In effect, a very similar fate befell I AM ERROR six years earlier, which became even disavowed by creator Roddenberry himself, before the franchise elevated the series to canon in 2006 for commercial reasons after Roddenberry had passed away. However, as was the case with the Animated Series' episode "Yesteryear", there was one episode of Galactica 1980 that was favorably received by fans and production staff alike, the series' finale "The Return of Starbuck", in which original Starbuck performer Dirk Benedict reprised his role as guest star, befriending a Cylon after both had crashed on a deserted planet, the only episode with a more or less mature theme, later explored in more depth in the small unnoticed, yet acclaimed 1985 science fiction movie Enemy Mine. A such, fans consider this episode only as semi-canon, much like their Star Trek counterparts do "Yesteryear"., consider Galactica 1980 to this day as non-
Following the cancellation of Galactica 1980, ABC commissioned Universal to re-edit the mult-part episodes of both Galactica series into twelve television movies, which it repeatedly aired in the early 1980's in order to recoup some of the production costs.  Unlike Star Trek in syndication however, this ploy failed to rekindle interest in the Galactica franchise.
Still, while considered "campy" by moderen audiences, the original series – as does Larson's Buck Rogers for that matter – retains to this day a relatively small, yet loyal, fanbase, both having attained a cult status in the process. Both these series are regularly re-issued on home media formats as complete collection editions, including on Blu-ray Discs, these brought forth by the success of re-imagined BSG. Unsurprisingly, Galactica 1980 is rarely re-issued and left out of the main series collection releases, though it has itself seen an one-time-only 2007 bare-bone (meaning no extras included) DVD release as the most recent one.
The perceived dismal performance of original BSG, combined with an all-time low interest for televised science fiction in the 1980s, and the near-similar per episode pricetag attached to it, were almost certainly the reasons for ABC to decline the new Star Trek: The Next Generation pitch, when Paramount Television CEO John Pike approached the studio six years later in 1986 in search of an outlet for the new show. (William Shatner Presents: Chaos on the Bridge) Yet, it was precisely The Next Generation that proved that a considerable science fiction television audience was still out there, when it soared in popularity around the turn of the decade, spawning two successful spin-off series of its own, Deep Space Nine and Voyager, in 1992 and 1994 respectively, and being joined on television in 1993 by a new, equally succesful science fiction franchise, Babylon 5. It is therefore not too much a stretch of the imagination to argue that The Next Generation heralded a new era of televised science fiction, as well as paving the way for re-imagined BSG.
Nonetheless, it took some time for minds to ripen to even consider revisiting BSG. First and foremost there was original BSG performer Richard Hatch, who had played the original Captain Apollo, one of the main characters in the original series. Though he had declined to reprise his role in Galactica 1980, having been sceptical of the premise of that series, he remained a staunch and vocal believer and supporter of the original series throughout the 1980s and 1990s. A frequent convention attendee, writer of several BSG tie-in books and novels, and founder of the battlestargalactica.com website, Hatch tried hard to keep the original series in the awareness of the public and studio. His efforts to get BSG back on the screen culminated in 1998 in the four minute, proof-of-concept, trailer Battlestar Galactica: The Second Coming, which he co-wrote/produced/starred in/directed, and comining in at a cost-price of US$20,000 paid for by himself.  Intended as a sequel to the original series, discounting Galactica 1980, it was received to great fan acclaim when shown at conventions. Featuring brand new CGI visual effects, Hatch also managed to enlist the help of several former BSG performers, including Star Trek performer Richard Lynch, who thereby gained the distinction of becoming one of only two performers to appear in all three original BSG live-action incarnations – the other one being original Colonel Tigh performer Terry Carter. Despite the fan acclaim though, and much to Hatch's frustration, the trailer failed to get the attention of Universal. Hatch himself though, was yet to make a significant contribution to the live-action franchise later on.
In hindsight, and unbeknowst to Hatch at the time, there was actually a reason for this. It turned out that Universal had let slip the BSG movie rights back to creator Larson, who subsequently was in the midst engaged in developing his own BSG sequel movie, called Battlestar Atlantis (in which Commander Cain and his battlestar Pegasus was slated to make a re-appearance), at the same time Hatch was busy with his. A simple trailer, only featuring graphics, was presented before Hatch's more professional one, but like Hatch's, Larson's proposal failed to gain traction as well. The reason for this in both cases was that Universal was still licking its wounds after the costly failure of their own ill-conceived 1993-1996 The Next Generation emulation attempt, seaQuest DSV – incidentally also served by some Star Trek alumni, past and future. (A Vision of the Future - Star Trek: Voyager, p. 54)
After Universal had regained the BSG rights, it contracted Star Trek performer and X-Men director Bryan Singer and Producer Tom DeSanto in January 2001 to develop a new BSG sequel series for their and, most ironically, Fox's television divisions, again discounting Galactica 1980. Announced on 22 February 2001 , Singer stated at the time, "[T]he Galactica brand is a sleeping giant. It was a show I watched during its initial run, from the pilot to the final episode. The essence and the brand name is quite potent in a climate where there's a great deficit of sci-fi programming."  The development however, was thwarted by the 9/11 terror attacks, and by the time the project could be taken up again, Singer was forced to decline further participation as he was committed to direct the second X-men movie and that the studio had already decided to go with the different concept of David Eick and Ronald D. Moore. Singer incidentally, shortly therafter conceived Star Trek: Federation, a spin-off proposal that was not developed either.
All these revival attempts were very reminiscent of the struggle Gene Roddenberry and others had to go through to get Star Trek back on the screen in the 1970s. (see: The Motion Picture: Production history)
Re-imagined Battlestar Galactica (2003-2012)
Prior revival attempts having come to naught and prompted on again by industry competitors to revisit its old science fiction property, it was only after the dismal failure of seaQuest DSV and the 9/11 Attacks, that Universal Studios decided in 2002 to start anew with a remake instead of a sequel as previously proposed. Despite being industry distribution partners, Universal had by then become one of the Hollywood studios that became increasingly envious of Paramount Pictures for its Star Trek franchise due to the property's stable and highly profitable revenue stream for that studio, particularly in the early-to-mid 1990s when Star Trek was at its peak in popularity, being Paramount's most profitable property for a period of time, admitted as such by them; Universal desperately wanted something like Star Trek of their own as well, and which had been the primary reason for the ill-fated seaQuest DSV project in the first place. (A Vision of the Future - Star Trek: Voyager, pp. 50-51, 54)
In service of that goal, Universal appointed Producer David Eick for its development as showrunner. Eick immediately sought out former Star Trek Writer/Producer Ronald D. Moore – who had been responsible for many of Star Trek's most popular episodes in the Berman-era, just like his predecessor Gene Coon had been on original Star Trek – to serve alongside him as such as equal. Eick reasoned that if anyone had a thorough understanding of what made a mature, modern science fiction show tick, it must have been Moore; seaQuest DSV had failed precisely because it did not tick. The franchise was succesfully relaunched on SyFy Channel (which continued to be the broadcaster for the subsequent remainder of the revamped franchise) with the 8-9 December 2003 two-part miniseries Battlestar Galactica, subtitled "Night, Part 1" and "Night, Part 2. The series was well received by both fans and critics, earning eight industry award nominations of which it won two, enticing the studio and broadcaster to continue with the production. Essentially one itself, the miniseries has, like Star Trek, seen several spin-off live-action productions, the 2004-2009 four season main series (into which the miniseries was incorporated as pilot episodes), four smaller webisodes series (delving deeper into the background of events referenced to in the main series) of which two (Razor and Battlestar Galactica: Blood & Chrome, in 2007 and 2012 respectively, the latter becoming the last live-action outing in the re-imagined franchise) were re-edited into feature length television movies, joining a specifically made third one (The Plan, 2009), and eventually the spin-off prequel series Caprica (2010). Coined "Re-imagined BSG", the renewed franchise became also frequently referred to as "Rebooted BSG" or "Revamped BSG", akin to the later alternate reality Star Trek films as produced by J.J. Abrams.
Like Gene Roddenberry before him on The Next Generation, the new BSG showrunners were legally obligated to bring in creator Glen Larson in an official capacity on the revamped show, because of his "created by" credit. Given the official "Consulting Producer" title, Larson however, unlike Roddenberry on The Next Generation, largely left the showrunners to their own devices, though he was consulted by them, asked for his input and generally kept in the loop, in stark contrast to Roddenberry when he was given a similar title – but no function – for the five subsequent Star Trek films following The Motion Picture.
The looks and settings modernized, and using imaginative cinematography for the space action scenes – a variation thereof also introduced in later live-action Star Trek, starting with the 2009 alternate reality movie Star Trek – , the miniseries largely followed the storyline of the 1978 original pilot episode/feature film, but the subsequent spin-offs, starting with the main series, differed substantially in story thematics from the more straightforward, superficial, somewhat "campy" – typical for television action shows of the 1970s-1980s era – and action driven ones of its progenitor. "Taking the series seriously" and incorporating lessons learned from 1990s television, the showrunners crafted episodes with more depth in which television audiences could see their own lives and the contemporay social issues they had to contend with reflected realistically in the lives and events of the series' characters in a mature manner. (The 2000's, S01E01: "The Platinum Age of Television") In this the showrunners followed in the footsteps of Moore's great example Gene Roddenberry, who had already intended something similar for both his Original and The Next Generation series. In order to focus on the human condition and human drama, the re-imagined franchise, contary to the original one, featured no aliens whatsoever.
Even the original alien Cylon race, were re-imagined as being human-created, and who have risen up against their makers, reflecting the growing ethical concerns in contemporary society about artificial intelligence as voiced by such luminaries as Stephen Hawking and Elon Musk.  Not only constructed as life-like humans (actually already foreshadowed in the unsuccessfull Galactica 1980 series, where a humanlike Cylon was introduced in the two-part episode "The Night the Cylons Landed"), the newest models were also burdened with human emotions, doubts and fallacies they have inherited from their creators, leading eventually up to a Cylon civil war. The particular theme of a robotic intelligence rising up againsts its creators only to go to war with itself, had actually already been explored in the prior Voyager season two episode "Prototype". In the even earlier The Next Generation season two episode "The Measure Of A Man", the difficult ethical question was postulated whether or not an artificial, yet sentient, lifeform remains the property of its creator, to be exploited at will by said creator – in re-imagined BSG the very reason for the uprising of the Cylons against their makers – , and was further explored in the prequel spin-off series Caprica, which dealt with the origin of the sentient Cylons. These two episodes therefore, foreshadowed in themselves the advent of re-imagined BSG.
There were however two major differences with Roddenberry's enlightened atheistic (human) universe; The basic premise itself, made BSG by default a far more darker and grittier universe – especially after the franchise was rebooted, with its thinly veiled references to among others, the 9/11 Attacks, the Iraq War and terrorism – , whereas religion played a major part in re-imagined BSG, particularly in Caprica, where religious intolerance and fanaticism served as social commentary on contemporary real world growing religious intolerance. Creator Larson had actually already incorporated subtle references to the Mormon faith, to which he belonged, in his original incarnation.  These references however were lost on non-believing viewers of the superficial, action driven original series.
Star Trek in Battlestar Galactica
In the miniseries, one of the "Rag Tag Refugee Fleet" ships had the call sign "Gemenon Traveler 1701". The colonial fleet also included a ship named Astral Queen, a reference to the ship of the same name in TOS: "The Conscience of the King". A Constitution-class starship is briefly visible in one shot of the colonial fleet in the miniseries. The footage is subsequently recycled in the first season opening credits, as well as selected stock footage in several episodes themselves.  
Moore has revealed that the first name of the "Kara – callsign: Starbuck – Thrace" character, one of the main protagonists from the revamped Battlestar Galactica, was inspired by Deep Space Nine's Kira Nerys, played by Nana Visitor.  Incidentally, for Moore's Galactica, the "Starbuck" part was recast as female from the original male character.
In the episode "The Ties That Bind" (S04E05), Colonel Tigh, Chief Tyrol, and Tory Foster meet in weapons locker "1701D", like the "Gemenon Traveler 1701" a reference to BSG show-runner Moore's previous Star Trek work, The Next Generation in particular.
In the Caprica spin-off series finale, "Apotheosis" (S01E19), right before landing Daniel Graystone's personal airplane can be seen flying past a large building featuring a banner which (apart from a new color scheme) is identical to a banner previously seen in the conference hall for the IME conference on Dekendi III in ENT: "Stigma". The large overlap in VFX crew between the two series had more than likely something to do with this.
Cast crossover appearances
Contrary to the original incarnation, the re-imagined franchise started its television run at the tailend of Berman-era Star Trek, and, excepting Rekha Sharma (who had a major recurrent role in re-imagined BSG), all other performers who appeared in both had already made their Star Trek appearances.
The revamped version's principal star Edward James Olmos' Hollywood Walk of Fame star is right next to that of Patrick Stewart. Amusingly and like Loyd Bridges had been previously in a similar case, Olmos had been invited to audition for the part of Jean-Luc Picard, before Stewart was ultimately cast for the role.  Olmos has been on record of being skeptical of the science fiction genre, particularly for its portrayal of aliens (and therefore declining the audition invitation), yet he was already in 1983 seriously considered for a role in Star Trek III: The Search for Spock, ironically for the part of the Klingon Kruge, on the express wish of Director Leonard Nimoy. Olmos only accepted his BSG role as Commander William Adama – played by Bonanza star Lorne Greene in the original franchise – , when it became apparent to him that the series was to be primarily drama-driven and not to feature any "outlandish" life forms. (Battlestar Galactica: The Complete Series Blu-ray-special features, "Cast And Crew Take A Look Back", "The Last Frakkin Special")
Noteworthy was that Bridges' original part as Commander Cain, had also been recast as a female for the new version with Michelle Forbes now playing the strong, but equally misguided Admiral Helena Cain.
Playing the part of a cancer patient in the season four episode "Faith", Nana Visitor was brought aboard on the express wish of writers David Weddle and Bradley Thompson, like Moore, former Deep Space Nine production staffers. According to Thompson, Visitor was the first person Weddle thought of after reading the script. According to Weddle, Moore attempted to cast Visitor in the previous season and jumped at the opportunity to cast her in this episode. "We have always thought she is a tremendous actress with great range," Weddle said. "We thought she could deliver an amazing performance in this particular role. She did not disappoint us."  Cast as Kira Nerys, Visitor was actually the replacement for Michelle Forbes, who had declined to reprise her The Next Generation alter ego role as the primary Bajoran character on the new Deep Space Nine show.
Roger Cross was slated to play the role of Tomas Vergis in Caprica and had actually played the role in several deleted scenes of the pilot episode, before the role was recast with John Pyper-Ferguson for unknown reasons.
Star Trek regular Dwight Schultz did not appear in any of the live action productions, but did voice a character in the November 2003 Battlestar Galactica roleplaying video game, set in the original universe and released one month before re-imagined BSG premiered. Original BSG actor Dirk Benedict also reprised his original Starbuck character as voice actor; Schultz was co-starring alongside regulars Benedict and Lance LeGault in the popular 1980s series The A-Team. Likewise, frequent Berman-era Star Trek guest star James Horan, lend his voice talents to the game as an older Adama.
|Actors who have appeared in Star Trek and re-imagined Battlestar Galactica.|
|Actor||Star Trek role||Star Trek episode/film||Date||Galactica role||Galactica episode/film||Date|
|Karen Austin||Doctor Kalandra||DS9: "Nor the Battle to the Strong"||21-10-1996||Lilly||Battlestar Galactica (2004): "Escape Velocity"||25-04-2008|
|Miral||VOY: "Barge of the Dead"||06-10-1999||Ruth||Caprica: "Caprica pilot"||22-01-2010|
|Bruce Davison||Jareth||VOY: "Remember"||09-10-1996||Dr. Michael Robert||Battlestar Galactica (2004): "The Woman King"||11-02-2007|
|Menos||ENT: "The Seventh"||06-11-2002|
|Michelle Forbes||Dara||TNG: "Half a Life"||06-05-1991||Admiral Helena Cain||Battlestar Galactica (2004): "Pegasus"; "Resurrection Ship, Part Ⅰ"; "Resurrection Ship, Part Ⅱ"|| 23-09-2005|
|Ensign/Lieutenant Ro Laren||8 TNG episodes: from "Ensign Ro" to "Preemptive Strike"|| 07-10-1991|
|Battlestar Galactica: Razor||24-11-2007|
|Paula Malcomson||Madeline Reed||ENT: "Silent Enemy"||16-01-2002||Amanda Graystone||19 Caprica episodes: from "Caprica pilot" to " Apotheosis"|| 22-01-2010|
|Brian Markinson||Vorin||TNG: "Homeward"||17-01-1994||Jordan Duram||13 Caprica episodes: from "Caprica pilot" to " Apotheosis"|| 22-01-2010|
|Lieutenant Pete Durst||VOY: "Cathexis", "Faces"|| 01-05-1995|
|Sulan||VOY: "Faces"||08-05-1995||Commander Silas Nash||Battlestar Galactica: Blood & Chrome||09-11-2012|
|Doctor Elias Giger||DS9: "In the Cards"||09-06-1997|
|John Pyper-Ferguson||Eli Hollander||TNG: "A Fistful of Datas"||09-11-1992||Captain Cole 'Stinger' Taylor||Battlestar Galactica (2004): "Pegasus"; "Resurrection Ship, Part Ⅰ"|| 23-09-2005|
|Tomas Vergis||6 Caprica episodes: from "Know Thy Enemy" to "Things We Lock Away"|| 05-03-2010|
|Tech Sergeant Xander Toth||Battlestar Galactica: Blood & Chrome||09-11-2012|
|Rekha Sharma|| Ellen Landry|
Ellen Landry (mirror)
|DIS: "Context Is for Kings", "The Butcher's Knife Cares Not for the Lamb's Cry", "What's Past Is Prologue"|| 01-10-2017|
|Tory Foster (Final Five Cylon Model)||32 Battlestar Galactica (2004) episodes: from "The Captain's Hand" to "Daybreak, Part III"|| 17-02-2006|
|Battlestar Galactica: The Plan||27-10-2009|
|Mark A. Sheppard||Leucon||VOY: "Child's Play"||08-03-2000||Romo Lampkin||7 Battlestar Galactica (2004) episodes: from "The Son Also Rises" to "Daybreak, Part III"|| 11-03-2007|
|Dean Stockwell||Colonel Grat||ENT: "Detained"||24-04-2002||(Brother) John Cavil (Cylon Model #1)||15 Battlestar Galactica (2004) episodes: from "Lay Down Your Burdens, Part Ⅰ" to "Daybreak, Part III"|| 03-03-2006|
|Battlestar Galactica: The Plan||27-10-2009|
|Shane Sweet||Mimetic simbiot of Commander Charles Tucker||ENT: "Similitude"||19-11-2003||Student||Caprica: "The Reins of a Waterfall"||05-02-2010|
|Kate Vernon||"Commander Valerie Archer"||VOY: "In the Flesh"||04-11-1998||Ellen Tigh (Final Five Cylon Model)||23 Battlestar Galactica (2004) episodes: from "Tigh Me Up, Tigh Me Down" to "Daybreak, Part III"|| 13-12-2004|
|Battlestar Galactica: The Plan||27-10-2009|
|Nana Visitor|| Major/Colonel Kira Nerys|
Intendant Kira Nerys (mirror)
|173 DS9 episodes: from "Emissary" to "What You Leave Behind"|| 03-01-1993|
|Emily Kowalski||Battlestar Galactica (2004): "Faith"||09-05-2008|
|Rick Worthy|| Automated Unit 3947|
Automated Commander 122
|VOY: "Prototype"||15-01-1996||Simon O'Neill (Cylon Model #4)||9 Battlestar Galactica (2004) episodes: from "The Farm" to "Daybreak, Part III"|| 12-08-2005|
|Kornan||DS9: "Soldiers of the Empire"||29-04-1997||Battlestar Galactica: The Plan||27-10-2009|
|Elloran officer||Star Trek: Insurrection||11-12-1998|
|Noah Lessing||VOY: , "Equinox", "Equinox, Part II"|| 12-05-1999|
|Jannar||10 ENT episodes: from "The Xindi" to "Zero Hour"|| 10-09-2003|
Production staff crossovers
That subtle references to Star Trek were on occasion sneaked into the Battlestar Galactica franchise should not come as a surprise as Moore was an unadulterated "trekkie" himself, having brought in his former Deep Space Nine co-workers David Weddle and Bradley Thompson as writers/producers to form the nucleus of his creative writing staff on Galactica, joined by collegues Jane Espenson (who eventually became showrunner on Caprica alongside Moore and Eick) and Michael Taylor from season three onward. After I AM ERROR had wrapped these staffers were shortly joined by longtime Star Trek director Allan Kroeker, who directed two episodes for Moore's Galactica, as did former Voyager regular cast member Roxann Dawson, who directed one episode of Caprica. Dawson's husband Eric already served as casting director for both series of re-imagined BSG. Duras performer Patrick Massett joined Moore's team on Caprica as writer/producer. Moore himself incidentally, made a cameo appearance at the end of the 2004 series finale "Daybreak, Part III".
Nor were Moore and his writing staff the only production staffers on the franchise with a strong Star Trek pedigree, not by a long shot. The VFX department in particular was heavily manned with many former Star Trek production staffers. First and foremost there was Gary Hutzel who served as VFX supervisor, just like he had on Star Trek, but now serving right from the start in 2003 as the most senior VFX staffer, becoming Moore's right hand as far as the VFX were concerned, serving even longer than Moore had, as the latter left before the franchise finished its run in 2012. After Star Trek prime temporarily ceased its existence in 2005 with the demise of Enterprise, the VFX department was, after the first season of the 2004 series, substantially strengthened with additional "refugees" from the Star Trek franchise, Doug Drexler and David Takemura the most senior ones, they now serving as Hutzel's right hands. Already staffed with several former Foundation Imaging employees, Zoic Studios, the VFX house for Battlestar Galactica, became inundated with digital artist, who had moved over from Eden FX, the last VFX house to serve Star Trek prime in the Berman-era. A far from exhaustive catalog of former Star Trek VFX staffers employed at Zoic, included such artists as Robert Bonchune, Lee Stringer, Pierre Drolet, Adam Lebowitz, Gabriel Koerner, David R. Morton, to name but a few. Like they had done for Star Trek, these staffers helped the Battlestar Galactica franchise to its slew of VFX Emmy Award wins and nominations. A mentionable Zoic Studios addition had been Digital Artist Fabio Passaro, a prolific prior and later Star Trek (non live-action) franchise contributor. 
An official "Map of the Twelve Colonies" was released by Quantum Mechanix in 2011, drawn by Star Trek: Star Charts creator Geoffrey Mandel. Four systems are depicted, in a 2×2 grid, designated Helios Alpha through Delta. The four maps are ordered on the chart following the same unusual pattern as the four quadrants of the Star Trek galaxy (i.e. clockwise from top left: Gamma, Delta, Beta, Alpha).
The favorable reception by fans and critics alike of the 2003 miniseries, was continued with its follow-up; The main series, including the television movie Razor and The Face of the Enemy webisode series, added no less than eighty-six industry award nominations to the ones already received for the miniseries, of which it won thirty-three in the timespan 2005-2009, besides numerous other media honors. Caprica added another seven nominations to the array, but this time only winning one of them. Remarkable was, despite the emphasis on the human conditions for which the primary cast was acclaimed in the media, that none of them received an Emmy Award in the "Actor" categories, or were even nominated as such. This re-imagined BSG had in common with Star Trek – though for the latter Leonard Nimoy had become the only actor ever to be nominated for one, and that cast member of both franchises did receive other awards in the "Actor" categories, the Saturn Awards in particular.
Nonetheless, a rift started to appear between fans and critics after the main series had concluded its run 2009. The movie The Plan, produced back-to-back with the main series was received with mixed feelings by fans, feeling it failed to deliver on explaining what the titular "plan" of the Cylons, mysteriously referred to in all the title cards of the main series, exactly entailed. Even more sceptical were fans of the prequel series Caprica. Even though showrunner Ron Moore took care not to include the Battlestar Galactica moniker in front of the series title – just like the showrunners had done for the first three seasons of Enterprise before him – in order to differentiate the series from the main one, and that critics were by and large favorable in their assessment of the series, precisely for its focus on the human condition, the majority of fans themselves were of a different mind – even though the series retained a small loyal fanbase of its own. Deeming the series, that featured virtually no space bound scenes, too far off the beaten track, viewership dropped from a high of 1.6 million viewers to less than 900,000 halfway through the series with rating droppings to match. In comparison, the main series started out with 3.1 million viewers.  But unlike their Star Trek counterparts had been with Enterprise and Nemesis, disenchanted BSG fans were not nearly as vehement or vocal in their disapproval, they simply tuned out or did not even to bother to tune in at all. Shy of five episodes, SyFy Channel cancelled the series before all episodes were even aired, though they were included on the later home media releases. In this re-imagined BSG resembled Babylon 5, the fierce Star Trek franchise competitor which had just finished its television run shortly before re-imagined BSG started its; Once the primary narrative had been told in both franchises' respective main series, fan interest started to wane sharply for the spin-off productions.
The by fans far better received movie Battlestar Galactica: Blood & Chrome, drawing in 1.2 million viewers when it was first aired by SyFy channel on 10 February 2013 and placed as a bridging narrative between Caprica and the main series, turned out to be the final coda for the re-imagined live-action franchise. Moore had by then already left, though many of his former co-workers on the franchise, including those with the Star Trek pedigree, stayed on for the coda. It was partner David Eick who headed that very last forray into the franchise. And in this re-imagined BSG resembled Enterprise; Facing dropping ratings and viewership, its last season saw a revival once other showrunners had taken over, though it did not save Star Trek prime from indefinite termination either for the time being.
Despite the critical acclaim, there were die-hard fans of the classic series, who denounced the re-imagined series right from the start, increasingly referring to the re-imagined franchise by the acronym "GINO"–Galactica In Name Only –, and these fans were subsequently joined by others, critical of the later BSG spin-off productions, Caprica in particular. It was precisely for this reason that Richard Hatch, the original Captain Apollo performer, was offered, and had accepted, a recurrent role – albeit cast as a different character, the terrorist turned politician Tom Zarek, a nod to the Irish IRA organization – on the revamped 2004 series in an effort to appease both sides of the fanbase by showing that he, the vocal defender of the original incarnation, endorsed the re-imagined series. (Battlestar Galactica: The Complete Series Blu-ray-special feature, "The Last Frakkin Special") In this, it has resembled the fan criticism that befell The Next Generation prior to, and during its first season, and the subsequent appearance on the show by Leonard Nimoy, in his case reprising his original role as Spock. And like in The Next Generation and beyond, more and more references to the original BSG, including the appearances of classic Cylon models and ships, were incorporated in re-imagined BSG too as production progressed, not only to appease the classic fanbase, but also because many production staffers were fans of the original as well, as was the case in Berman-era Star Trek, including Moore, Bonchune, Hutzel and Drexler themselves.
Moore himself reacted to this criticism with humor when he made a cameo appearance in the "A Space Oddity" episode of the crime series CSI: Crime Scene Investigation (S09E20, 2009) – incidentally co-written by his former Next Generation writing colleague Naren Shankar; the subplot in that episode involved a young director/producer remaking an old science fiction series with a brand new concept, angering fans with Moore, as a convention attendee, being the first person to speak out in order to denounce the remake.
In contrast to the original incarnation, and the somewhat lackluster reception of The Plan and Caprica notwithstanding, Universal Studios was pleased with re-imagined BSG and entered into negotiations with creator Larson for a remake of the original 1978 theatrical feature in February 2009, one month before the re-imagined main series ended its run on 20 March. ("Universal in talks for 'Battlestar' movie", The Hollywood Reporter, 20 February 2009) Essentially slated to become a third live-action incarnation of the BSG franchise, Bryan Singer was for a second time contracted as director/co-producer in August 2009 for the project ("Bryan Singer to direct 'Battlestar' film", The Hollywood Reporter, 13 August 2009), who subsequently commented after a 12 August 2012 script rewrite, "It will exist, I think, quite well between the Glen Larson and Ron Moore universes."  However, development was slow and Singer had to again leave the project due to other motion picture obligations. The project appears to be still in the development stage, as Universal has appointed a new team of producers, writers and director in 2016.  Creator Glen Larson (3 January 1937 – 14 November 2014; age 77) is no longer involved either, because of his passing in 2014.
Less well fared broadcaster SyFy Channel after re-imagined BSG had finished its run. As the first of its "SyFy Original Series", the broadcaster seemed to be taken offguard by its huge succes, and failed to deliver afterwards in the public eye, causing the broadcaster to slip considerably in ratings for an extended period of time. It took the broadcaster over six years of restructring and rethinking its formula in order to slowly finds its way up again. 
Similar in concept to the 2006 40 Years of Star Trek: The Collection Star Trek auction, Alec Peters managed to secure for his auction house Propworx, Inc. the commission from Universal to auction off the series' production assets, after the main series of re-imagined BSG had wrapped, in two specialized auctions held on 17-18 January, and on 8-10 May 2009 at The Pasadena Convention Center, followed up by a third, smaller 27 August 2011 one after Caprica too was cancelled in 2010.  Based on the strenght of their BSG auctions, Propworx became in 2010 also the commissioned auctioneer for the assets of the defunct Star Trek: The Experience attraction as well. Also starting in that year were a series of smaller specialized Star Trek auctions, in which Propworx auctioned off the production assets retained/saved by former Star Trek production staffers, including those of concurrent former BSG production staffers such as Doug Drexler as well as Gary Hutzel in the more recent ones.
In the popular, heavily Star Trek referencing, sitcom The Big Bang Theory (S04E04: "The Hot Troll Deviation", 2010) lead actress Katee Sackoff has made an appearance as her Galactica alter ego Starbuck, conjured up by series' principal character Howard Wolowitz, who has the hots for Starbuck. Sackoff/Starbuck, miffed at being the object of adulescent sexual fantasies – having already appeared as a figment of his overheated imgination in the prior episode "The Vengeance Formulation" (S03E09) – , tries to gives Wolowitz romantic advise but is shortly thereafter joined by an equally imaginary George Takei in his Hikaru Sulu outfit from Star Trek IV: The Voyage Home, trying to do the same. Sackoff/Starbuck starts bickering with Takei/Sulu, questioning his credentials to give Wolowitz romantic advise, while poking fun at Takei's homosexuality. Both however, are also lamenting and exchanging notes on being typecast as Starbuck and Sulu respectively.
In stark contrast to the Star Wars and Babylon 5 franchises, rivalry between the fanbases of Battlestar Galactica and Star Trek had been comparatively light, if there had been any to speak of at all. The reasons for this can arguably be found in the disparity between the two basic premises, the fact that – the last season of Enterprise excepted – there had been no overlap of first time airings, the large overlap of former Star Trek production staff in re-imagined BSG, the circumstance that re-imagined BSG temporarily served as a refuge for "trekkies" disenchanted with Enterprise/Nemesis, or any combination thereof.
That the Battlestar Galactica fanbase has become more modest than its Star Trek counterpart, became evident in September 2015, when the webmaster of the original Battlestar Wiki announced, "Due to diminishing interest in BSG and the fact that most of the main contributors have since moved on, I am looking at the possibly of shutting down the website come early next year." By March the following year the Wiki, at the time featuring 4,528 articles, had indeed gone dark.  Nonetheless, fans by then had saved a large part, but not all (about a quarter was lost), of its contents on the Wayback Machine internet archive. Two new, from the ground up rebuilt, and different Battlestar Galactica Wikis went up a year later, though featuring far less content.
The disparities between the two fanbases notwithstanding, there are several franchise licensees who have served both with their merchandise, which included such companies as, besides Quantum Mechanix, FASA , Revell-Monogram, Eaglemoss Collections and Hasbro.
Prolific Star Trek reference book authors Mark A. Altman and his writing partner Edward Gross have authored an exhaustive work on the history of the entire BSG live-action franchise as well, modeled after their recent The Fifty-Year Mission: The First 25 Years and The Fifty-Year Mission: The Next 25 Years Star Trek live-action franchise histories. The 720-page work, titled So Say We All: The Complete, Uncensored, Unauthorized Oral History of Battlestar Galactica (ISBN 9781250128942), was released on 21 August 2018. "So Say We All" refers to an improvised expression introduced in the re-imagined miniseries by Edward James Olmos, going on to become a staple in the subsequent BSG productions. Like Star Trek's "Beam me up, Scotty" has before, it became a popular popculture catchphrase as well.
– incomplete archived original Battlestar Galactica wiki
- Battlestar Wiki – cloned live version of the archived original Battlestar Galactica wiki featuring 3,534 articles
- Battlestar Galactica at Wikipedia
- Galactica TV – Behind-the-Scenes info site with Ralph McQuarrie and Andrew Probert concept art
- Star Trek and Battlestar Galactica: Understanding Politics and International Relations at thing.iafor.org, The Academic Platform