Continuity mistake: In the school near the end, one of the dead guys looks through the round window into the library and says 'wow'. In the long shot from within the library, his face isn't in the window. Back to the shot of the window, he's still there.
Continuity mistake: Whenever we see the two Willows together in this episode we see that Vampire Willow is understandably very pale in comparison to the living Willow. However, in the library with Cordelia, when Vampire Willow says 'How about dinner?' her face is no longer pale.
Continuity mistake: When Buffy wakes up in the hospital bed you can you can see the black strap of her tank top underneath the gown. Then when she gets out of bed on walk to Faith, and it shows her walking through the hall you can see a white spaghetti top through the gown.
Visible crew/equipment: Just after Cordelia says "let's go to the Bronze", check the top of the screen - a microphone drops into shot for Harmony's line "is that a joke?" (00:16:20)
Continuity mistake: After Buffy is supposed to meet Willow and she is walking home you can see she is wearing light blue wedge heels but when she is down in the basement she is wearing completely different purple heels.
Continuity mistake: Lily's boyfriend is taken into an alternate dimension, where time moves quicker than ours, and is kept there until he is an old man. But when Buffy finds him, she realizes who he is because of his tattoo - which has not faded or aged in any way. (00:23:20 - 00:34:30)
Revealing mistake: After Faith brings Angelus back, when she goes to punch him and he blocks, the stuntman switch is very obvious - he's noticeably taller, has different hair and doesn't even seem to be wearing any vampire make-up.
Continuity mistake: In the episode 'Anne' when the latest people to be brought into hell are lined up with a demon talking to them, there are 3 or 4 people standing between Buffy and Lily. When the demon asks them all in turn 'Who are you?' we see him asking Lily and after that the shot rests on Buffy, but in the background we only hear him ask one more person before he gets to Buffy. (00:35:50)
Continuity mistake: When the detective is interviewing the woman in the alley, he mentions that the murder took place "last night". In "Bad Girls", we see Buffy visiting Faith the day after the murder, and that night is presumably when she has the dream about drowning, so by the time the detective is asking this question it is actually two nights after the murder, not one.
Continuity mistake: When Wesley and Cordelia kiss, after a few seconds they freeze in place. Cordelia has her left arm around his waist, we see a shot of her face for about a second with her arm definitely angled downwards, then we cut to Wes' face and her hand's now on his neck. (00:25:20)
Visible crew/equipment: In the scene where Buffy is packing Joyce's clothes into a suitcase you can see a mic moving at the top of the shot as they walk through the door.
Lover's Walk - S3-E8
Continuity mistake: In the scene where Xander and Willow are stuck in the factory Xander wakes up you'll notice that the blood on his side burn closest to his ear constantly changes lengths from shot to shot. It goes from under the chin to slightly below where the blood on the other side of his side burn is. (00:30:30)
Continuity mistake: In the scene where Buffy has just finished fighting the demons, she begins climbing up chains and if you look at her shoes, they continue to change until she reaches the ground above the chains and runs off. (00:40:30)
Other mistake: In "Doppelgangland", Vampire Willow struggles to remember Cordelia's name. However, it is still Willow, she knew Cordelia from being human (we see this in The Wish as well).
Other mistake: When the detective is interviewing the woman in the alley he says "So you heard the man scream about what time?", but Finch didn't scream as he died.
Revealing mistake: In Graduation Day Part One, when Faith shoots Angel with the longbow, you can see the false point spring out as if it were on a hinge from inside his jacket. (00:22:47)
Continuity mistake: In 'Consequences' Buffy says to Faith 'Less that 24 hours ago you killed a man'. In 'Bad Girls', Faith kills Finch in the alley on the first night. One night later Buffy and Angel are attacking Belthazor, the night after that is the night when Buffy dreams about drowning, so the night when Buffy says this is actually about 72 hours after the murder. (00:11:25)
Plot hole: When Buffy enters the house to rescue her mother she uses a stake to stop the front door from closing. A vampire then grabs it and the door closes. Why did Buffy use a stake knowing that there was a vampire there when she was almost killed by a vampire with her own stake earlier in the episode because Giles had been injecting her with a muscle relaxant?
Lover's Walk - S3-E8
Revealing mistake: Early on, Spike falls down drunk. He wakes up because his hand is on fire from the sunlight. When he runs away, a little bit of fire stays on the stones where his hand was when it started.
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.