Star Trek: Deep Space Nine and Babylon 5 were involved in a controversy in the early 1990s, with DS9 accused of plagiarism by Babylon 5 fans. Deep Space Nine was the 3rd series in the Star Trek franchise and ran from 1993 to 1999. The plot focused on the crew of the Federation space station Deep Space 9, commanded by Benjamin Sisko. The series is noted for being a departure from the traditional Star Trek model, both in the sense that it was set on a space station instead of a starship and that many of its plotlines were focused on noticeably darker themes, such as war, genocide, and a host of morally ambiguous issues.
Created by acclaimed screenwriter and producer J. Michael Straczynski, Babylon 5 was also a show about the human and alien crew of a space station that gave the show its name and was set in a tumultuous region of space. In addition to this, the two shows shared a number of other similarities in regards to characters and plotlines. Both had human captains who became the prominent religious figures of an alien race, and very similar villains in the form of Star Trek: DS9's the Dominion and Babylon 5's the Shadows, both of whom attempt to take over through military prowess and sneaky political manipulation in their respective series.
Since Babylon 5 premiered after Deep Space Nine, it might seem surprising that the Star Trek show was the one accused of plagiarism. However, while it is true that Babylon 5 did not premiere until 1994, it had been in development for a number of years before that. Straczynski had pitched the show to several different production companies, one of which was Paramount Studios, the company the owned Star Trek. During the pitch, Straczynski had given Paramount some reference materials including a show Bible, which Paramount had kept even after rejecting Babylon 5. It was not long after this that Paramount announced they were developing Star Trek: Deep Space Nine, and when details about the show's plot began to surface, the similarities to Babylon 5 lead Straczynski to speculate that Paramount had used his Bible when developing their new series.
Straczynski made it clear that he did not believe that Deep Space Nine creators Rick Berman and Michael Piller had directly plagiarized him, a sentiment that was echoed by Berman and Piller themselves who said they had never heard of Straczynski or his work. However, Straczynski maintained a belief that Paramount had been influenced by his pitch for Babylon 5, although he declined to pursue any formal legal action against the studio, feeling that a court case would negatively impact both TV series. Because of this, there was never very much animosity between Deep Space Nine and Babylon 5's creative teams after the initial matter was dealt with. Babylon 5 even employed a few well-known Star Trek actors such as Walter Koenig and Majel Barrett-Roddenberry, who supposedly guest-starred on the show as a gesture of goodwill after the controversy.
However, the relationship between the two fanbases was not so easily put to bed, and both entered into a rivalry that has never entirely gone away. Babylon 5 fans continued to accuse Deep Space Nine of plagiarism, and Star Trek fans became derisive of Babylon 5 as a result. While the similarities between the two shows are undeniable, both have gone on to receive critical acclaim and developed distinct identities separate from each other. It is certainly possible that Paramount was in some way influenced by Babylon 5, but even Straczynski seemed to feel direct plagiarism was very unlikely. In the end, the controversy between Star Trek: Deep Space Nine and Babylon 5 was made a much bigger deal by the fans of both shows than by either set of creators.