One of Star Trek VI: The Undiscovered Country’s more curious additions is Lt. Valeris, a Vulcan Starfleet officer played by Kim Cattrall and serving as the protégé for Leonard Nimoy’s Mr. Spock. She ultimately betrays him and the rest of the crew in the name of a conspiracy trying to derail peace talks between the Federation and the Klingon Empire. She ties into the film’s notions about fearing change; an ostensibly heroic Starfleet officer who would rather destroy her enemies than make peace with them. Cattrall’s strong performance was a part of the film’s winning formula, and remains well-regarded among Star Trek fans.
And yet the character is still an obvious stand-in for another beloved figure, Lt. Saavik -- another Vulcan protégé of Spock’s with a memorable run through the movie “trilogy” of Star Trek II: The Wrath of Khan, Star Trek III: The Search for Spock and Star Trek IV: The Voyage Home. Saavik would have made a natural addition to Star Trek VI, and her status as a franchise stalwart would have hammered her betrayal home even harder. Instead, she remained absent and a new character was created. The reasons why owe a lot to both the fluidity of what the movies were attempting, and fears of alienating the fan base.
Lt. Saavik began with The Wrath of Khan and director Nicholas Meyer is generally credited with her creation. According to the DVD commentary for the movie, he had all but decided on casting Cattrall as Saavik when the actor signed with another project and became unavailable. Kirstie Alley was cast instead, and made an instant splash in the role. Her status as a younger Starfleet officer in the midst of the aging original crew worked well, tying into the film's notions of growing older and passing on the torch.
Alley lost the role to Robin Curtis in The Search for Spock after demanding an increase in salary that the production could not afford. Curtis’ version of the character was much different, and though she made an outstanding Vulcan, some fans struggled to get over the disparity. According to the Blu-ray commentary for The Voyage Home Blu-ray, she was written out after a brief coda because she felt extraneous to the plot, and the character never appeared in canon form again. Fans have since embraced Curtis’ take on Saavik, and the character has continued to appear in off-canon stories such as novels and comics.
That left Saavik in an interesting position once the development of Star Trek VI began. Meyer returned to direct, and the behind-the-scenes book The Making of the Trek Films states that early drafts of the script had Saavik, not Valeris, betraying the Federation. Gene Roddenberry reportedly disliked the idea – feeling, with some reason, that fans loved the character too much – but Meyer went ahead with the notion. Saavik possessed an onscreen backstory that enhanced the impact of her betrayal, as well as emphasizing how difficult the crew found it to set their enmity of the Klingons aside and accept peace.
The problem, again, came to casting. Meyer didn’t care for Curtis in the role – Leonard Nimoy had directed the actor in Star Trek III and IV – and wanted to restore Alley. Alley, however, had been starring on Cheers since 1987. It was one of the biggest hits on television at the time, and if her asking price was too high before, it was well beyond their budget now. Rather than recasting a second time, they decided to change the character completely. Cattrall, a near-miss for the part the first time, made an easy choice for the new character.
The problem was that Valeris became a figure of convenience as a result. Her background as Spock’s trusted confidante is taken as a given, but without any onscreen development of the kind Saavik enjoyed in Star Trek II and III, her connection to the other characters feels pro forma. She exists essentially to betray the crew, but without knowing more about her earlier, the audience can’t feel the sting of her betrayal nearly as much. The character’s superficial similarities – and Curtis’ presumed availability – made Saavik a better fit for the film. Valeris is strong in every way except the one that matters most: her past with the crew and the way she betrays that in the name of a perceived greater good. The background can’t be faked, and both she and the movie are a little diminished as a result.