Reptile Boy - S2-E5
Continuity mistake: When Buffy is at the party, we see that she is wearing black shoes with a high heel. But when she is fighting Machida, the heels are considerably lower.
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)
Plot hole: Giles tells Willow to leave him while he extracts information from Ethan on how to break the costume spell. By the time Giles smashes the statue Willow has already found the others, who had left the house where she thought they were and are hiding in a completely different area of the town. No matter how long it took Giles to beat the information out of Ethan, there is no way Willow could have gotten back to the house, realised they were gone and tracked them down before the spell was broken. As a ghost, it is possible she could have happened across them even though they were hiding, but seems unlikely.
The Dark Age - S2-E8
Continuity mistake: Cordelia tells the Scoobies that Giles was talking to the police about a homicide, but this wasn't mentioned in the time that she was in the room. (00:18:15)
The Dark Age - S2-E8
Continuity mistake: At the end of the episode, Buffy complains to Willow and Xander that she will have to blow her allowance on getting the tattoo removed before her Mom sees it. Moments later when Buffy is talking to Giles, the tattoo is gone. (00:40:45 - 00:42:30)
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)
The Dark Age - S2-E8
Continuity mistake: When Giles is making calls in his apartment, he takes his glasses off and drops them on the desk, just above the notebook with his list of names. But in the close up of the notebook, the glasses are now on the top of the notebook.
Continuity mistake: When Buffy is fighting Kendra the fragments of the table she is thrown onto have disappeared when she stands up again. (00:42:40)
Revealing mistake: Although the mirror in Buffy's room is mostly covered by photos, Angel's reflection can be seen for a split second as he walks past it to pick up the photo of Buffy ice-skating.
Continuity mistake: When they ask about the demon that Xander and Cordelia encountered in Buffy's basement, Xander points to the bug that Cordelia threw from her hair onto the open book. He then slams it shut. A shot later, the book is gone.
Continuity mistake: When Buffy's mom sets down the carton of orange juice on the table after the golf trip, watch closely. The continuity is nightmarish. The carton rotates multiple times between cuts. The cap is on, then off, then back on again between cuts. And Buffy's mom's hand keeps moving on and off the carton between cuts.
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.