Audio problem: When Giles and Miss Calender are walking through the halls at the beginning of the episode there's a kid at the vending machine, we hear the coins rattling but he never puts money into the slot. In fact, the money doesn't go anywhere near the slot.
Audio problem: When Jenny and Giles are talking and Jenny is talking about the festival, they walk behind a drinks machine and then her lips don't match up with what she says.
Continuity mistake: After Buffy finds Morgan's brain, Willow pulls up Morgan's school file on one of the library computers without even touching the keyboard. One moment the monitor is on the desktop, the next it's showing Morgan's file.
School Hard - S2-E3
Vampire: And when I kill her, it will be the greatest event since the crucifixion. And I should know, I was there.
Spike: You were there?! If every vampire who said he was actually at the crucifixion really was there, it would've been like Woodstock!
The Freshman - S4-E1
Trivia: At the Bronze, Buffy sees someone whom she thinks is Angel. Until his face becomes visible, revealing it's someone else, the man she sees is played by David Boreanaz.
Question: Specific answer needed, not a general "dialogue is sometimes re-recorded". Near the start of this episode, Buffy's talking to Giles about the significance of the earthquake. Buffy's dialogue sounds completely normal and recorded at the time, but all of Giles' dialogue is dubbed. I can only think he had a sore throat that day or similar, but does anyone know the specific reason he did his later?
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.