Revealing mistake: When we see Spike and Andrew on Spike's motorcycle talking about Onion Blossoms, a filming light is reflected in Andrew's helmet.
End Of Days - S7-E21
Revealing mistake: When Buffy finds Faith and the Potentials in the sewers she throws an Ubervamp across the room. When we see the Ubervamp from behind you can also see the actor's blue boxer shorts sticking out of the Ubervamp costume.
Revealing mistake: Early in the final fight, Vi makes a flying kick to knock an Ubervamp off the cliff. As she lands, she swings back and twists slightly, suspiciously like one would do if suspended on a wire. There is no way she could gain this motion by kicking straight off the vamp as shown. (00:29:00)
Revealing mistake: In the last episode, 'Chosen', Anya beheads two Ubervamps. The second time she swings the sword it very noticably doesn't go anywhere near the Ubervamp's neck, closer to its stomach.
Chosen answer: He had larangitis and because of the shooting specifications they had to have him shoot the scene with a bad throat, they then re-recorded his lines and dubbed them. At various points during the scene and indeed the episode you can see him touch his throat or rub it.