Kirstie Alley had a different approach to Lt. Saavik when she starred in Star Trek II: The Wrath of Khan. She brought emotions to the character, even crying at Spock's funeral. Star Trek fans weren't necessarily fans of her showing those emotions, and that all changed when Robin Curtis took over the role for Alley in Star Trek III: The Search's for Spock.
According to Curtis, who appeared on the SciFi Diner podcast [via Slashfilm], her portrayal of the Vulcan lieutenant was based upon direction from the movie's director, Leonard Nimoy. She admitted she wasn't a Star Trek fan and knew nothing about Vulcans. But Nimoy wasn't concerned and simply told her he'd "take her every step of the way."
""When people comment on the subtle differences or perhaps some of the more obvious differences between the two portrayals, I have to remind them I think it's very much a collaboration between the artist and the director, for sure. Obviously, Nicholas Meyer and Kirstie kind of went to the edges of the emotion and the flirtation, and they brought some nuances to the character that Leonard Nimoy would have no part of. He didn't want me to breathe in the wrong place, as much as I tried to inject that little layer of emotion. It wasn't happening. He wasn't having it." "Robin Curtis
Curtis thought who better to guide her than the man who'd made Vulcans famous? And she clarified that Nimoy was very strict when it came to emotions. He didn't want her inputting any into the character, unlike what Alley was allowed to do by The Wrath of Khan director, Nicholas Meyer. Curtis admitted she tried to inject some emotion to her character, but Nimoy wouldn't allow it. So she followed his lead, making Saavik much more stoic and vastly different from Alley's version of the Vulcan.
Leonard Nimoy knew about Spock. He knew what made the Vulcans work and how they should act. Clearly, he didn't want Curtis stepping over the line so he kept tight control of how she was supposed to act...which is how Star Trek fans expect Vulcans to act. No one could say that Nimoy didn't know what he was doing when it came to directing or Vulcans.