Character mistake: When Spock beams down after calculating there was just enough energy left for him to do so, Sulu and Kirk watch him materialize, and Sulu says, "Someone beaming down from the bridge." From the bridge? Shouldn't he have said "from the ship"? No one ever beamed down directly from the bridge, but even if they could, how would Sulu know that's where they'd come from?
Continuity mistake: Don Juan tears Yeoman Barrows' tunic at the right shoulder. Near the end, when she changes from the fairy tale dress back into the tunic, the torn right shoulder is suddenly mended. They're cut off from the ship by the power drain, so she couldn't have beamed up for a new one. She emerges from the bushes after changing, and now her tunic is torn at the left shoulder.