Star Trek's abandoned Spock replacement character, the Vulcan named Xon, may now be a part of Star Trek canon thanks to the latest episode of Star Trek: Lower Decks. This week's episode of Star Trek: Lower Decks, titled "Crisis Point," is a send-up of the Star Trek film series, which has a decidedly different tone than the Star Trek film universe. There are references to Star Trek: The Motion Picture's notoriously long, lingering reveal of the updated USS Enterprise design, the lens flare in the modern movies, and how the films play fast and loose with the rules of transporter technology.
The episode's plot sees Ensign Mariner turning Ensign Boimler's holodeck program into a Star Trek movie starring Lower Decks' crew. But Mariner jokingly tells Boimler that she doesn't think he'll "make the final cut" of her film. To illustrate the point, she compares Boimler to Xon. When Boimler says he doesn't know who Xon is, Mariner tells him that's the point.
So who is Xon? He's a character that never made into Star Trek canon despite being cast for the first-ever Star Trek spinoff. David Gautreaux would have played the Vulcan in Star Trek: Phase II, a Star Trek sequel series concocted in the 1970s. But that never came to pass. The studio abandoned plans for the show to make Star Trek: The Motion Picture instead, which used ideas from Phase II as its basis.
As the story goes, Phase II would have brought back most of the cast of Star Trek: The Original Series, but Leonard Nimoy would only have reprised his role as Spock in two of the show's 13 proposed episodes. Nimoy was insulted by the offer, though later wrote in his second memoir that he might have been giving off the impression that he wanted to distance himself from the role at the time. Either way, Nimoy rejected the offer, and Star Trek creator Gene Roddenberry came up with a new character to fill the void.
That character was Xon, the Enterprise's new science officer, played by Gautreaux. Though a full-blooded Vulcan instead of a half-Vulcan, half-human like Spock, Xon would have been more curious about human behavior than his predecessor and less zealously dedicated to repressing his emotions. Gautreaux got into costume and makeup for the role, and footage from his screen test still exists, but he never appeared in a Star Trek show or movie. That's because once the project became a movie instead of a television show, Nimoy agreed to reprise the role of Spock. Xon became redundant, and the writers cut him from the script.
Despite being written out, Xon does have a legacy in Star Trek that goes beyond Phase II and The Motion Picture. Xon became the template for Data in Star Trek: The Next Generation. Star Trek also later explored a full-blooded Vulcan serving alongside humans on a Starfleet vessel through T'Pol in Star Trek: Enterprise.
The bit about Xon in "Crisis Point" is a meta-humor for the fans, but Lower Decks is still Star Trek canon. The episode may suggest that the Xon of Phase II does exist in the Star Trek Universe. Perhaps he even had a role to play at some point in the adventures of the USS Enterprise under Captain Kirk only to be "written out" of the popular version of Starfleet history.
Star Trek: Lower Decks is streaming now on CBS All Access. The season finale debuts Thursday.