Revealing mistake: One of the arrows that Spike gets hit with passes through just below his left shoulder, but there are times when you can tell that it is a fake arrow because the part of the arrow sticking out at the front moves and the part at the back does not. Look at the arrow just after Buffy turns Hus into a bear.
Buffy The Vampire Slayer (1997)
1 revealing mistake in Pangs
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?
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.