Trivia: In the episode 'The Replacement' Buffy asks what they're going to do with the 2 Xanders who then say 'Kill us both Spock'. This is a reference to an episode of Star Trek where Kirk ended up with an evil twin and Spock didn't know which one to kill, the real Kirk told Spock to kill them both so Spock killed the other one.
Trivia: In the episode 'The Replacement' when Xander is trying to convince Willow that he is the real Xander, he does the Snoopy dance for her. Nicholas Brendon didn't know what the snoopy dance looked like and just attempted it after a brief description. He is now frequently asked to perform it at any fan conventions he attends.