Revelations - S3-E7
Revealing mistake: In 'Revelations' when Buffy and Faith are fighting, the kick Faith aims at Buffy's face right after she says 'We can work this out' very noticeably misses, but Buffy still reacts as though it landed. (00:36:15)
Revealing mistake: Several times during Spike's escape from The Initiative, his reflection can be seen in the glass. Vampires aren't supposed to have reflections. (00:13:00)
Revealing mistake: As Buffy throws Spike into a wall after he bites Andrew, Spike's stuntman is visible in-shot. His hair is slightly different to James Marsters'.
Revelations - S3-E7
Revealing mistake: When Gwendolyn Post fights Angel in the mansion, she breaks a long-handled shovel over her knee to create a stake. If you watch in slow motion, the handle of the shovel is pre-broken (she simply holds the two pieces together tightly), and the pieces separate just before they actually make contact with her knee. (00:34:55)
Revealing mistake: When Anya sings her song about how she will become Mrs. Harris, she spins Xander's chair around after putting a blanket on him. When she is also sitting on the chair, and you see an overhead shot of them both, you can see a section of the stage floor rotating beneath them keeping the chair spinning.
Revealing mistake: Near the end, the TV behind Andrew shows the periscope's view, but it doesn't match the movements he makes with it. (00:36:25)
Revealing mistake: When all the vampires are saying "for the dark", and one gets staked, there's a mark on his shirt where the stake's about to come through before it actually happens. Plus Buffy's hands are in the wrong place for her to have pushed that stake through, as well as there being no stake in her hand when the vampire gets dusted. Not only that, but the mark isn't even close to the vampire's heart to begin with. (00:34:50)
Revealing mistake: At the very beginning of the episode, Lyle's reflection can be seen in the tiles on the floor in the shopping mall.
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.
I Only Have Eyes For You - S2-E19
Revealing mistake: After Buffy has entered the wasp-filled school there's a shot of the others standing outside waiting for her. In the establishing long shot if you look closely you can see they used the same shot as earlier in the episode - Buffy is standing there with them. (00:34:10)
Revealing mistake: When Buffy sets the vampire alight, his face suddenly gets very shiny, showing the fireproof gel that was applied to the actor's skin. (00:37:20)
Revealing mistake: When Buffy saves the man from being hit by a car, there is a very quick shot of the man standing in front of the car. In this shot, Buffy can seen on the left hand side of the screen running into the street to save him. But the shot then immediately cuts to Buffy who is suddenly still standing on the other side of the street with Lily and runs into the street to save him again.
Revealing mistake: At the start of the episode where Warren, Jonathan and Andrew are on quad bikes chasing two vampires, a shot of the two vampires running towards the camera is used twice.
Revealing mistake: After Buffy leaves the cave where Adam kills Forrest, she trips and falls down a horizontal slope. She then rolls over some rocks and one of the rocks wobbles.
Revealing mistake: During Faith's fight outside the Bronze in 'Faith, Hope And Trick' when she stakes the vampire, if you watch carefully, you can see the rubber stake bending. (00:15:20)
The Dark Age - S2-E8
Revealing mistake: When Buffy and Giles are talking in the school in the final scene, the same extra (in a beige shirt and blue jeans) walks out of the room behind Buffy twice. (00:42:50)
Once More, With Feeling - S6-E7
Revealing mistake: During the song-and-dance number "They Got The Mustard Out", if you look closely at the dancers, the man in green to camera right of the second row is horribly out of step with the music, and with the rest of the group. The spell makes everyone dance far better than they naturally would (Tara loses the clumsiness she often displays, for example), so it is a mistake to have someone under the spell dancing so badly.
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.