Continuity mistake: When Jenny meets Giles after Xander's botched attempt at asking out Buffy, the way she's holding the folders to her chest subtly changes repeatedly between the closeup and wide shots.
Continuity mistake: When Buffy turns down Xander's date proposal at the start of the episode, throughout the scene, Xander has his backpack up around his right shoulder. However, when he walks away, it's instantly down by his side.
Visible crew/equipment: When Buffy meets Giles in the library after the opening credits, and they start talking, throughout the scene, you can see set lights and reflectors reflected in Giles' glasses multiple times. This happens often throughout the series, but is particularly noticeable here.
Revealing mistake: When Willow says "The usual " at the beginning of the episode and it cuts to Buffy landing on the ground, you can briefly but see the stunt woman playing Buffy's face in the first shot for a solid second or two. That definitely isn't Sarah Michelle Gellar.
Continuity mistake: In the beginning, when Xander is practicing asking Buffy out with Willow, at once point Willow puts one of her snacks (candies, I think) into her mouth and starts chewing in a medium/wide profile shot of the two. It then cuts to a closeup of her and instantly she's no longer chewing, and immediately places a second candy in her mouth. She didn't have time to stop chewing and swallow between cuts.
Continuity mistake: When the earthquake happens at the start of the episode, and we see the Master celebrating, his hands instantly change positions at least twice between cuts. (Sometimes it matches perfectly between cuts other times they're in an entirely different position between cuts).
Continuity mistake: When Buffy stakes the first vampire at the beginning, in the first shot, his hands are in towards his abdomen. When the camera cuts behind him, and he falls back, suddenly they're instantly extended partially outwards to either side.
Continuity mistake: When Cordy stops kissing her boyfriend and says "What was that?" at the beginning of the episode, the lighting on Cordy's face changes completely as it cuts between the two camera angles. In the first angle, the lighting is much darker and shadowy, while in the second angle, her face is suddenly much brighter.
Continuity mistake: Joyce is driving Buffy to school and she is wearing a pink tank top. At school that day her shirt is white, but the next day at school she is back to wearing the pink outfit. (00:15:50)
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: As Willow, Cordy, Miss. Calendar and Giles are wheeled over the bones of the Master, Giles goes past and his hand brushes against the bones - the skeleton bends, revealing that it is rubber. (00:36:10)
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)
Continuity mistake: In the season two episode, 'When She Was Bad', in the scene where Buffy smashes the masters skeleton with a sledge-hammer she smashes the rib cage to pieces. Suddenly the rib cage has again become completely intact and she smashes it to hell again. (00:40:35)
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.
Revealing mistake: In the scene where Absalom is speaking of the Anointed one, the line can be seen where the vampire makeup meets up with his real face. This may be seen in various scenes he is in.
Continuity mistake: At the end of the episode when Buffy is talking to Giles about how she can't face her friends, her hair is over her ears for the entire conversation, but when she is about to walk away, her hair is suddenly tucked behind her ear and she couldn't have tucked it behind as that side of her head is still in view when the camera's on Giles.
Other mistake: At the end of the episode Willow mentions going to the Bronze on a Wednesday night, Buffy also mentions to Giles that she got almost everyone killed on the second day of school. From the different clothing being worn each day, it's obviously been more than 2 school days and should instead be Thursday by the end of the episode.
Revealing mistake: When Buffy is fighting the vampires that are trying to resurrect The Master, at one point she is grabbed from behind by a male vampire and kicks a female vampire in a green top twice (right after Absalom shouts "The sacrifices! Stop them!"). If you watch closely, both of the kicks miss the vampire, revealing that the fight was choreographed. The punch that she delivers to the male vampire afterwards also looks fake.
Some Assembly Required - S2-E2
Continuity mistake: In the episode 'Some Assembly Required' Eric takes photos of Cordelia and Buffy near the start, when he's developing them later the poses in the photos are different to the way the girls were standing at the time. (00:06:40 - 00:19:05)
Chosen answer: Angel is saying that he is still jealous and Buffy recognizes that this is his way of saying he wishes that they could be together. That is why they both smile.