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.
Continuity mistake: While studying at the Bronze, Buffy and Willow leave their books on the table to go and dance. Spike calls them outside to fight a vampire, and when Xander runs back inside to grab a stake the books have all been put back into Buffy's bag.
00:14:00 - 00:15:45
Continuity mistake: 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.
00:23:15 - 00:29:20
Continuity mistake: 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.
Continuity mistake: In 'Becoming, part 1' as Buffy kneels over Kendra's corpse you can see the door over her shoulder, it stays closed all the time. There is a cut to a shot of Buffy from behind showing a cop raising his gun, but he couldn't have come through the door without us seeing him in the last shot.
Continuity mistake: When Buffy's fighting Spike at the end of the episode, there are times when it's obvious that it's James Marsters' stunt double. Spike's hair is platinum blonde, slicked back, and all one length in the back, while the stunt double's hair is more brassy, spiked in the front, and layered in the back.
Continuity mistake: In "Becoming Part 2" At the end when Spike chokes Drusilla unconscious, he picks her up, one of her hands is resting on her stomach and the other is hanging to her side. It cuts to a shot of Spike looking at Angel and Buffy fighting then to Spike leaving with his back facing the camera. You can see that the hand resting on Drusilla's stomach moved to Spike's shoulder.
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.
Continuity mistake: 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 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.
Continuity mistake: According to Giles in 'Revelations' there are 12 cemeteries in Sunnydale, but in 'Becoming Part 1', amongst others, Buffy agrees to meet someone (Angelus in this case) in 'the cemetery'. If there are 12 in the city, how would they know which one she means?
Continuity mistake: 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.
Continuity mistake: When Cordelia is being tied up in the corridor, Buffy leaps up, kicks the attacker, and drops to the ground next to Cordelia. In the next shot the attacker is stumbling to his feet, and Buffy is standing again, then quickly kneels down beside Cordy.