J.J. Abrams rebooted Star Trek in 2009 with a new cast of actors, and it's actually a good thing that William Shatner hasn't appeared in Abrams' alternate Kelvin Timeline. Although Star Trek has established itself as one of the greatest sci-fi franchises of all time, none of its characters have quite reached the same level of pop-culture relevance as those of The Original Series. Chief among that cast of characters was William Shatner's Captain Kirk and Leonard Nimoy's Mr. Spock, and the pair have remained iconic in the generations since the show's initial run.
J.J. Abrams rebooted the franchise in 2009 with a film written to take place in an alternate timeline, allowing him to recast the roles and tell a story free from the constraints of Star Trek's decades of continuity. Considered Star Trek's Kelvin Timeline—named after the Federation starship U.S.S. Kelvin that was destroyed at the start of the Star Trek reboot—Abrams' film spawned two sequels, with a fourth film reportedly on the way. Of The Original Series' cast, only Leonard Nimoy appeared briefly within Abrams' continuity in order to explain how the alternate timeline was formed and to offer a passing of the torch moment for the new cast.
Initially, Abrams considered involving Shatner in the Kelvin Timeline, too. The idea ultimately never came to pass, and Nimoy's brief appearance as Spock Prime worked perfectly within Abrams' new continuity, but it's actually a good thing that Shatner didn't make an appearance as Kirk Prime. Not only would his character have offered a much different insight than Nimoy's, but his conditions for appearing would have potentially derailed the tone of Abrams' franchise.
William Shatner's Planned Role In Star Trek (2009)
The original plan was for Shatner to return to the role of Kirk for Star Trek, acting in a very similar capacity to that of Spock Prime. A scene was written for Shatner to appear via a holo-recording of a message he'd recorded for Spock Prime, used as a means of proving the existence of the alternate reality from which Nimoy's Spock had traveled. The scene as it was written would have allowed for Shatner to make a small but meaningful cameo in the film, but still adhere to the canon in which Kirk Prime was dead.
Unfortunately, this reportedly wasn't right for Shatner. J.J. Abrams made it clear that Shatner wanted his involvement to be more substantial, and that he was vocally opposed to his role being that of a small cameo appearance. According to Abrams, when he considered James T. Kirk's backstory and history, and Shatner's willingness to be a larger part of the film, he realized that there would be no way to organically include him without betraying the vision of his reboot.
Abrams' Original Shatner Idea Wouldn't Have Worked
While Abrams' original idea to incorporate an appearance from Shatner into his new timeline was honorable, it was doomed to fail. As Abrams would later identify himself, including Kirk Prime would warrant giving the character far more attention, which in turn would have shifted the focus away from the reboot's cast. What's more, Abrams' movies taking place in a separate continuity allowed for a departure from Star Trek's main canon, and Kirk Prime's appearance would have risked undermining what made that work.
Shatner's planned appearance in Star Trek's Kelvin Timeline would have had Kirk Prime read a vague message to Spock which also served as something of a goodbye to the franchise he helped build. This would have surely been a touching moment, but it would have taken away from the emotional impact of Nimoy's own appearance. What's more, having multiple characters from Star Trek's Prime Universe make appearances in the alternate timeline would have further blurred the line between the two. As the Abrams movies thrive on their separation from the canon of The Original Series, Kirk Prime's appearance would have been ill-advised.
Chris Pine's Kirk Deserves To Be Separate From Shatner's
There's another factor that would have seen Shatner's Captain Kirk return in Star Trek hurt the reboot, and that's in the way it would have impacted Chris Pine's own version of the character. While the planned cameo for Shatner wouldn't have had too great an impact, Shatner's insistence that he be given a larger role would ultimately have hurt Pine's iteration of James T. Kirk. Had Shatner appeared in 2009's Star Trek in any significant way, it would have drawn additional comparisons between the two actors' performances.
Chris Pine's version of the character is very different from Shatner's. The idea behind this is that Pine's version has an entirely different backstory than Kirk Prime, meaning that the two characters are effectively separate people, even within the canon of Star Trek's Kelvin Timeline. Pine's performance has helped the Star Trek reboot movies thrive, and also updated the ideology behind Shatner's performance, making the character more human. Direct comparisons between the two would only serve to divide the audience, which would ultimately have hurt the film.
Why Nimoy's Spock Prime Was The Perfect Character To Cross Over
William Shatner's cameo appearance in Star Trek may never have come to pass, but Leonard Nimoy still appeared as Spock Prime. The alternate timeline was created by the presence of Nimoy's character, making his role pivotal in the creation of the Kelvin Timeline. However, it's not just that his role in establishing the canon of the newer series of Star Trek movies was perfect for Spock Prime - Nimoy's character was actually the most logical choice to do so.
Of all of The Original Series' cast, Nimoy and Shatner are the only two actors that could conceivably be considered its leads. It was an important mark of authenticity to have one of the two appear in the reboot, and Nimoy was far happier to take on a smaller role than Shatner. However, Spock himself is a far better choice to explain the science behind how the alternate timeline was formed, and as Star Trek's story revolves around Romulans hunting Spock Prime, the choice to have Leonard Nimoy's Spock meet Zachary Quinto's made perfect sense.
Will Other Original Series Actors Appear In Star Trek's Kelvin Timeline?
So far, Nimoy is the only Original Series actor to cross over into the Kelvin Timeline. With Star Trek 4 reportedly on the way, it's possible that other Star Trek actors may appear, but it's unlikely that they'll reprise their roles from The Original Series. The logical basis for the separate timelines essentially prevents this from happening, although, within Star Trek's sci-fi future, it seems that almost anything is possible - including time travel and travel between universes. So far, the Kelvin Timeline has proved an easy entry point to the franchise for those uninitiated in the wider canon of Star Trek. By keeping its story generally separate from that of the Prime Universe, this mass appeal endures, so including appearances from Original Series actors is something that Abrams will likely avoid. In fact, had he included William Shatner in his Star Trek reboot, the franchise may have turned out very differently.