Revealing mistake: Throughout almost the entire sword fight between Buffy and Angel, from the far away shots, its clear that the actors are stunt doubles. It's very visible when there is a shot from the top. (00:34:05)
Revealing mistake: When Buffy and Angel are sword-fighting, the camera pans up and to the side, you can see David Boreanaz's stunt double. His hair line is farther back then David Boreanaz's.
Continuity mistake: Willow is turned into a ghost. Throughout the entire episode, she can't touch anything (can't turn the pages of a book, etc.), yet towards the end when she and Giles go to Ethan's shop, and she leaves, you can hear that she opened and closed the door, even though she can walk through walls and can't actually touch the door. The curtain moves when she leaves too. (00:34:05)
[After saving Giles from a vampire.]
Spike: Awww, poor Watcher. Did your life flash before your eyes? Cup of tea, cup of tea, almost-got-shagged, cup of tea?
Band Candy - S3-E6
Trivia: The accent that Giles uses as his teenage self is Anthony Head's natural accent.
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.