Both Leonard Nimoy and DeForest Kelley famously rejected starring in Star Trek Generations and they had good reasons for skipping the TNG movie.
Although Star Trek Generations saw the return of the original series star William Shatner, the iconic actor wasn’t joined by colleagues Leonard Nimoy and DeForest Kelley. Instead, Shatner appeared alongside Walter Koenig and James Doohan, who reprised their roles as Chekov and Scott respectively. Paramount Studio’s original plan was for the entire cast of Star Trek: The Original Series to appear in Generations in order to pass the torch to the TNG crew. However, it soon became clear that several original members were unhappy at the prospect.
Released in 1994, Star Trek Generations marked Star Trek: The Next Generation’s leap to the big screen. Not only was it the first and only meeting between Shatner’s Captain James T. Kirk and Patrick Stewart’s Captain Jean-Luc Picard, but Star Trek Generations also climaxed with the death of Captain Kirk. As the screenplay took shape, it became clear that other TOS legends would appear in the film’s prologue set in the 23rd century, with Kirk moving into the 24th century to meet Picard and heroically die fighting the film’s villain, Dr. Tolian Soran (Malcolm McDowell).