Continuity: 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.

Revealing: At the very beginning of the episode, Lyle's reflection can be seen in the tiles on the floor in the shopping mall.

Continuity: When Buffy puts her egg down, the position of the chain and pen she sets it down by change depending on whether the shot's from Willow's side or Buffy's.

Other: In this episode, Buffy says that Drusilla could be alive because they 'never saw her body'. Drusilla is a vampire; if she was dead, there wouldn't be a body to see - as the slayer, Buffy knows this.

Continuity: Near the beginning when Buffy and Willow are talking about Willow getting together with Oz, Buffy's hair is in front of her ears. Then she turns to face Willow to say, "You think he's too old 'cause he's a senior? My boyfriend had a bicentennial," and in that shot change, her hair switches to behind her ear then goes back to being in front of her ears in the next shot without her every touching her hair.

Factual error: In the season two episode 'Surprise,' when Buffy and Angel escape from Spike, Dru and the Judge they jump down into the sewer. That is fine, except that they run all of five metres and then go up the ladder to escape. However, when they come out of the sewer they are in a very open area with the factory nowhere in sight. They have not travelled far enough for this to be the case.

Continuity: When Buffy wakes up she is wearing metallic nail polish, yet when she went to sleep previously, she has no nail polish on. Later in a scene where Buffy is dreaming about her night with Angel she has the nail polish on again, even though that took place the night before when she did not have her nails painted.

Continuity: In Innocence, when the Scoobies are in the library, Oz (I think) says for the crew to meet outside Xander's house a half hour later. Then we cut to Buffy strolling through Sunnydale High in broad daylight, then back to Oz's van outside the military base and it's last night again.

Continuity: The book that Cordelia replaced sideways in the bookshelf behind her disappears, and then reappears just before she and Xander kiss.

Revealing: Drusilla's reflection can be seen in the metal part of what appears to be the base of a shopping mall map just as she's getting up after the Judge has been blown up.

Continuity: When the Judge is blown up, Drusilla and Angel leap from the balcony. In mid-air, they somersault and their backs are facing the ground as they fall, but a second later they land on their stomachs.

Continuity: When Buffy is told that Angel has become Angelus, she mentions "I should have known. When I saw him at the house he was different", but her earlier conversation with him took place not at the house but at his apartment. This isn't just a strange turn of phrase - the scene was originally shot at the Summers house, but was changed to Angel's apartment for more emotional resonance.

Revealing: In the scene where Drusilla and the new reformed Angelus are in the shopping mall and they got blown over the side after Buffy fires the grenade launcher at the Judge, you can tell that it was Mike Mass and not David Boreanaz that got blown over the side.

Continuity: Second season, episode Phases. Willow is escaping from Oz the werewolf and runs into the library, where Giles is. In the first shot, he isn't wearing his glasses, then in the next shot he is, then he isn't, then again in the next shot he is.

Revealing: In season 2 Phases where Oz finds out he is a werewolf in the seen where Giles is driving Buffy to the Bronze if you look closely you can see people's heads pushing the car because it had broke down

Continuity: In the episode 'Phases', season 2, when Willow is running from the werewolf she falls and there's a big mud stain on her pants. In the next scene when she runs into the library it's gone.

Visible crew/equipment: In the episode in season 2 where Oz is found to be a werewolf right after Kane and Buffy's fight in the woods, in the shot right after Kane leaves, you can see set-lights above the clearing where they fought.

Deliberate "mistake": After Jenny pushes the janitor's cart into Angelus and runs up the stairs, there's no physical way he could be waiting for her at the top of the stairs (even with vampiric speed). Joss Whedon has admitted in interviews that he put in this blatant continuity error as the situation is a staple of the horror genre (girl runs from villain, only to find him standing right in front of her).

Continuity: In the computer room, Jenny asks Angel how he got into the school. Earlier in the series, Spike's gang attacked the school without being invited in. Jenny would have known about this and therefore should have known that vampires can get in.

Continuity: In the episode 'Killed By Death', when Buffy looks into the childrens' ward the sign on the door saying 'Basement Access' disappears and reappears between shots.