Revealing mistake: Early in the movie Samantha is in the rec room watching TV, she briefly watches Jay Leno who is dressed in a brown suit, with a brown & white striped tie. Much later in the movie James is in his room watching TV, and he briefly watches Jay Leno, who is dressed in the same suit and tie. It appears Jay Leno doesn't change his suits often.
Continuity mistake: In the scene at the end when Samantha is kissing James and a little before that, you can see that Samantha's bun is quite low on her head and so is the tiara. It is so low that it cannot be seen from Samantha's front. After she walks outside (within 60 seconds of the kiss) the bun is higher up on her head and the tiara is visible from the front.