Revealing mistake: Near the end of the "Bendee-Boo" segment, while everyone is laughing, one of the Harlem Globetrotters' (between Amy and Leela) right arm keeps disappearing and reappearing several times in one shot.
Other mistake: Bender wears a magnetic bow tie. However in series 1 episode 2 it's shown magnets screw up his circuits and make him sing songs. It's mentioned in a previous entries correction that it's only when the magnet is near his head. This isn't true as it's shown in others episodes that it happens when a magnet is attached anywhere on him.