Lover's Walk - S3-E8
Continuity mistake: In the episode Lover's Walk, when Spike is threatening Willow at the factory, in the long shots Willow's hair is up over her face, and in the close-ups it isn't. The pointed bit of the bottle is at the top or bottom in different shots too. (00:19:20)
Continuity mistake: As Buffy is being trained at the register, the receipt at the top of the register switches in every shot. (00:07:45)
The Weight Of The World - S5-E21
Continuity mistake: When Glory is griping about human emotion, her arms change between wide shots and closeups. (00:23:00)
Revealing mistake: Several times during Spike's escape from The Initiative, his reflection can be seen in the glass. Vampires aren't supposed to have reflections. (00:13:00)
Continuity mistake: When Buffy, Willow, and Dawn are discussing Riley's problems in the bedroom, Dawn's hair shifts from over her shoulder in the long shots to behind her shoulder in the closeups. (00:16:45)
Visible crew/equipment: In the episode "Into The Woods" at the very end you see shots of Buffy and Riley from both the helicopter and the ground. The 2nd shot of the helicopter you can see a camera in the top right corner of the chopper. (00:40:35)
Continuity mistake: During season 7 we are told several times that the First cannot take corporeal form, ie. it cannot touch things. However, in its first appearance in the season 3 episode 'Amends', when it manifests as Jenny Calender and runs its fingers through Angel's hair you can see his hair moving underneath her fingers. It wouldn't be able to do this if it weren't corporeal. (00:15:50)
The Freshman - S4-E1
Continuity mistake: When Buffy is fighting the vampires at the end of the episode, she grabs a tennis racket and smashes the brunette vampire over the head. She falls over the back of the couch and we hear the thud of her landing, however in the wide shot of the couch the vampire has just started to go over the back.
Gingerbread - S3-E11
Continuity mistake: In the previous episode 'Amends', Buffy was sporting a brand new short fringe. In this episode it has grown out. Completely.
Deliberate mistake: While it is established that Angel doesn't age, it's obvious across both Buffy and Angel that David Boreanaz gets older. More unavoidable than deliberate, but still worth noting.
Bewitched, Bothered And Bewildered - S2-E16
Other mistake: Joyce tells Cordelia to grab some bandages for Xander from the bathroom upstairs. Joyce and Xander are in the kitchen and there is a small corridor that leads to the stairs, but Cordelia goes around the other way leading to the living room. Fair enough, Cordelia made a mistake. She isn't that bright. But she returns with the bandages coming back from the living room. Why come downstairs and then go All The Way around through the living room when she could have just walked down the small corridor?
Visible crew/equipment: When Willow and Dawn are running away from the demon, Willow uses magic to unlock a car for them to escape in. On the right side of the screen, shadows of crew members can be see as the car's doors open and are gone when Willow uses magic to make the car drive away.
Life Serial - S6-E5
Continuity mistake: When Buffy and Spike are in his crypt drinking whiskey, after Buffy says to him, "You have had so too much to drink at this point, I am cuttin' you off", she drinks a shot twice between shots.
Other mistake: At the beginning of the episode when Giles visits the archaeologists who have obtained the obelisk, it appears to be much too tall/wide to have fit through the door.
Continuity mistake: When Buffy has told the Scoobies her plan about going down into the Hellmouth, Willow starts talking about how it's beyond anything she's ever done. As she says this she is looking in Buffy's direction, but as she continues and the camera cuts away, her reflection can be seen in a nearby mirror - she is suddenly looking straight ahead of her and then turns to look in Giles' direction. She is then suddenly looking back in Buffy's direction as the camera cuts back to her.
Visible crew/equipment: When Dawn and the Potentials try to get past one of the police officers at The Bronze, Kennedy says that he'll have to shoot them all to stop them. As he responds with "It doesn't really bother me", the shadow of a boom mic can be seen on the wall behind him in the top right hand corner of the screen.
Other mistake: When The First (disguised as Eve) tells the Turok-Han to kill everybody except Buffy, it runs past her towards the exit of the crypt. The First then says, "Well, alone again", turns to face Spike and transforms into Buffy. In this shot, the Turok-Han can be seen still leaving the crypt, even though it had plenty of time to reach the exit and was running towards it at full speed.
Revealing mistake: As Buffy throws Spike into a wall after he bites Andrew, Spike's stuntman is visible in-shot. His hair is slightly different to James Marsters'.
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.