I definitely heard the story that Kirstie Alley wanted to be in Star Trek III, but she or her agent asked for too much money and blew the negotiation. There was a Starlog interview where she said (approximately) "She's not Saavik, I'm Saavik!" in the headline. Alley didn't reject the role, she missed out on it— that's what I understood it to be.
To clarify, I was only talking about why Alley didn't return as Saavik for
Star Trek VI, not III. That's a whole different thing.
I remember a
Starlog article promoting STIII that said although Alley's agents asked for a salary increase for the sequel, they apparently asked for too high a price and it was actually more than what DeForest Kelley was making for III (although they had no way of knowing that, of course). Alley ended up doing a stage production of
Cat on a Hot Tin Roof instead. You'd think she'd want to be in the film, considering that she was already a
Star Trek fan and TWOK was a hit. And outside of some reported clashes with Mr. Shatner, I don't think she had a bad experience doing the film or anything.
Honestly, it's so strange that Paramount never had the foresight to lock the cast down for sequels with standardized contracts, forcing the studio to renegotiate with them each time. But I guess they were always assuming that each new
Star Trek film would be the last one.
So making Curtis's Saavik seem above it all, unengaging and dull, not only hurt the character, it contradicted what had come before. An "unexplainable" mistake like that can often be explained if there is a hidden motive. Nimoy may have thought Spock came across as the "second most interesting Vulcan" in Star Trek II, that he was upstaged by Alley's fresh, vivid, realistic character, and he didn't want that to happen again. So yeah, I can see the possible motive.
It was really a bit of a revelation when I was listening to one of the commentary tracks for TSFS and Curtis talked about how Nimoy had directed her and I was just cringing because of how I felt it was sabotaging the character's potential, especially relative to Alley's portrayal.
I still don't want to believe it was intentional sabotage on his part, but...it's possible.
Yeah, I don't want to believe that Nimoy was that petty, either, but it's certainly possible. But who knows? Maybe he just had an entirely different interpretation of Saavik than Meyer and Alley did. But since, from what I understand, Saavik was a pretty popular addition in TWOK, that's a strange choice. Why mess with success?
But intentionally or not, I think it's pretty fair to say that Nimoy's direction killed off most of Saavik's potential. I remember Harve Bennett saying that they wrote her out of STIV so quickly because Saavik in the 20th Century would've just been "another pair of pointed ears to hide." Quite a comedown from the character's debut just two films before.