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For this film, Gene Roddenberry was given a consultant position, and replaced as executive producer by Harve Bennett. Apparently, Paramount Studios blamed the constant production delays and budget overruns for Star Trek: The Motion Picture (1979) on Roddenberry's constant meddling and demanding script rewrites. While the studio had been open to letting him produce the film, on the condition that he take a less hands-on role and share the producer's role with Jon Povill, who had been associate producer on the previous film, Roddenberry refused the notion of anything less than full creative control, and so was removed altogether from active involvement in the film.
The famous "Space, the final frontier" monologue is heard for the first time since Star Trek (1966), now narrated by Leonard Nimoy, however this has been changed slightly. Instead of saying, "...its five-year mission..." and "to seek out new life," this now says, "her ongoing mission..." and "to seek out new lifeforms".
Leonard Nimoy did not know about the final shot of Spock's coffin on the surface of the Genesis Planet. He first saw this at the premiere, and has said that his first thought was "I'm going to be getting a call from Paramount!"
In the Blu-ray special feature "The Captain's Log", Ricardo Montalban says that once he committed to this film, he realized that he had trouble getting back into the character Khan. After years of playing Mr. Roarke on Fantasy Island (1977), he found that he was "stuck" in that character. He requested a tape of Space Seed (1967) from Paramount Studios, and proceeded to watch it repeatedly. By the third or fourth watching, he had recaptured the essence of Khan's character.
Several episodes of Star Trek: The Animated Series (1973) had revisited previous episodes of Star Trek (1966), and this inspired the makers to produce a movie that would be a follow-up to a Star Trek (1966) episode. Producer Harve Bennett viewed all 79 episodes, and chose Space Seed (1967) as the best candidate for a sequel; Spock even remarks at the end that it would be interesting to return in a hundred years or so to see what type of civilization had grown there. This is the first time a feature film was made as a sequel to a specific television series episode.
After reluctantly being convinced to appear in the first film, Leonard Nimoy initially had no interest in a second. Harve Bennett finally convinced Nimoy to sign onto the film with the offer of having a death scene.
James Horner: running down a corridor during the preparation for the final battle, just before the torpedoes are loaded into the launch bay.