Lt. Saavik originally had a different purpose in Star Trek: Wrath of Khan
By now, Star Trek fans know that once upon a time Lt. Saavik was going to be pregnant with Spock’s child which is why she remained on Vulcan when the Enterprise left in the stolen Bird of Prey. That idea was jettisoned, and there was no real reason given for the lieutenant’s decision to stay on her home planet. There was, however, an explanation given for her presence in the Star Trek: Wrath of Khan script written by Samuel Peeples.
According to Forgotten Trek, originally, Saavik was to have been a child of Spock and the Romulan commander from “The Enterprise Incident” from Star Trek: The Original Series. The commander was to have been artificially inseminated and then, after the birth of Saavik, sent her to live on Vulcan.
Lt. Saavik’s parentage was supposed to be a source of drama
Peeples believed the duality of Saavik’s nature would have provided a ripe source of drama for the movie as she would have constantly been struggling against the two sides of her nature. She wouldn’t have been ruled strictly by logic because of her Romulan side, and that would have potentially lined up some issues between her and her father.
While seeing Spock as a father of this full-grown lieutenant under his command might have been interesting, the premise of the Romulan commander sending her daughter to live on Vulcan doesn’t quite work. Why wouldn’t the commander have wanted Saavik raised on Romulus? And with the anger she had against Spock, as well as the desire for revenge, raising his daughter to hate him would have made perfect sense. Instead, she hands her daughter over to Vulcan where Saavick excels and joins Starfleet?
There were so many unaired plans for Saavik, including a potential love affair with Admiral Kirk’s son, David, that it seems like the writers didn’t quite know what to do with her. There were definitely missed opportunities as she was a great character and could have added more to the movies. Instead, she was left behind on Vulcan.