Christian Slater was given lines meant for Grace Lee Whitney
The Star Trek franchise isn’t at a loss for fans, even in the celebrity world. And many of those celebrities want a chance to be a part, no matter how small, of Star Trek. Mick Fleetwood, for instance, drummer and co-founder of Fleetwood Mac, was even willing to be unrecognizable when he portrayed an Antedian dignitary (a fish-like alien) on an episode of Star Trek: The Next Generation. But Christian Slater had a more recognizable role in Star Trek VI: The Undiscovered Country.
When Slater’s mother was hired to cast the move, Slater used her job as his inroad to get a role on the movie. He asked her to help him get a spot, and she was able to fulfill his request. Slater was cast in a small role denoted as as “Excelsior Communications Officer.” He came onscreen long enough to wake up Captain Sulu to tell him that Starfleet wanted any data the Excelsior had on the whereabouts of the Enterprise.
Grace Lee Whitney didn’t get enough screen time
Originally, according to Screen Rant, those lines were supposed to go Grace Lee Whitney’s Janice Rand. Given the lack of screen time Whitney got in the films as well and the brevity of her time on Star Trek: The Original Series, it’s a shame that she was replaced in this scene by a celebrity who had already gotten more time on a movie screen than Whitney ever would.
Whitney was given the same title, Excelsior Communications Officer, as Slater but not much of anything else. Fortunately, Whitney was able to return to Star Trek as Commander Janice Rand on an episode of Star Trek: Voyager five years later, guest-starring alongside George Takei who portrayed Captain Sulu of the Excelsior.