Star Trek: The Original Series in syndication. Surprisingly, Spock actor Leonard Nimoy was only offered an appearance in two out of the planned thirteen episodes.
The reason for Nimoy's reduced involvement is unclear, but the actor believed that his memoir I Am Not Spock may have played a small role in giving his Star Trek castmates, Gene Roddenberry and Paramount the impression that he no longer wanted to be involved. A new Vulcan character named Xon was created, to be played by the actor David Gautreaux, who sat in for costume and make-up tests. When Phase II was aborted in favor of a theatrically released movie director Robert Wise insisted that Spock feature in the movie the plans for Xon had to change.
What Happened To Spock's Replacements In Star Trek: The Motion Picture
Xon was written out of the Motion Picture script, and actor David Gautreaux was given a different role. Sadly for Gautreaux, his new role wasn't nearly as substantial as the one he would have played in Phase II or a Nimoy-less Motion Picture. He was instead given a small part as Commander Branch, the Starfleet officer who witnessed the Klingons being destroyed by V'Ger. It must be strange for Gautreaux to know that his most notable credit as an actor is as a replacement for Spock in an abandoned Star Trek revival.
Spock also had a potential replacement in the fiction of Star Trek: The Motion Picture in the form of Commander Sonak. The new Vulcan senior science officer on the Enterprise would have followed in the footsteps of Spock, if it wasn't for a horrifying accident. In one of The Motion Picture's most disturbing scenes, Kirk (William Shatner) attempts to stabilize their transfer, but is unable to stop Sonak and their crewmate from having their genetic code fatally deformed by the process. In the face of this loss, Kirk observes he would prefer another Vulcan in Sonak's now vacant position, hinting at the eventual return of Spock.
Star Trek: The Motion Picture Wouldn’t Have Worked Without Spock
Spock is crucial to the first Star Trek movie because it's his failed spiritual quest that provides the emotional arc of the movie. In reuniting the TOS crew a decade later, The Motion Picture is a movie about finding meaning in later life. In his opening scenes, Spock fails the Vulcan kolinahr ritual, which is designed to purge all emotions. As the Enterprise's investigation of the V'Ger crisis continues, Spock feels an affinity with the sentient former satellite, as he too is questioning his very existence.
The first Star Trek movie works because the crux of the film's existential exploration of meaning is linked directly to Spock. If it had been Xon, a new character unfamiliar to fans and audiences alike, then it wouldn't have had the same emotional impact. The scene when Spock cries at finally encountering V'Ger doesn't have the same punch if it's just another Star Trek: The Motion Picture may be unloved in certain corners of fandom, but without Leonard Nimoy's performance, it would have been much worse.