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: The first night that the Gentlemen float through the college, they are on the 2nd floor one minute (all the room numbers start with 2), then they turn a corner and are suddenly outside room 118, a floor below.
Continuity mistake: When Buffy is giving her speech about being chosen, there is a shot of Andrew sitting on the couch next to Xander and Anya, but in several of the shots of the Potentials he can be seen standing on the other side of the room in front of the curtains. It's definitely him - his face isn't visible, but the clothes are the exact same.
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? (00:35:40)
Tabula Rasa - S6-E8
Continuity mistake: When Anya is standing on the table, wide shots show her holding the spellbook in front of her, but closeups show her holding it tight to her chest. (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)
The Harsh Light Of Day - S4-E3
Continuity mistake: When Buffy and Spike are fighting on campus during the day, Xander tries to help Buffy but Spike throws him against a lamppost. When he lands in the ground he falls completely on the grass on his side but if you look behind Spike in the next shot he lies half on and half on the grass on his front.
Continuity mistake: Where Willow is pulling the bricks out of the jail near the beginning of the episode. When she first pulls the bricks out of the arch thing they are from a different area than when you see the arch from the inside of the jail, even allowing it to be 'inside out' (as seen from outside and then the inside).
Continuity mistake: Ampata tells Buffy she has no lipstick, but earlier that episode we saw her using lipstick, in the high school bathroom right before the bodyguard attacked her. (00:24:20 - 00:25:40)
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.
Dead Things - S6-E13
Continuity mistake: In the episode (series six) where Buffy thinks she killed Warren's ex-girlfriend, when she's at the police station, in the over the shoulder shot of Desk Sergeant, he is holding the phone between his shoulder and ear. But in the front shot of him the phone has jumped to his hand. (00:36:45)
Reptile Boy - S2-E5
Continuity mistake: When Buffy is at the party, we see that she is wearing black shoes with a high heel. But when she is fighting Machida, the heels are considerably lower.
Get It Done - S7-E15
Continuity mistake: In the episode 'Get It Done' when Dawn and Buffy find Chloe's corpse the door across the hall from them is open. When it cuts back to them after the ad break it is shut, but there has been no time lapse.
Continuity mistake: After Buffy finds Dr. Gregory's glasses at the start of Miss French's class and places them on the table, they move position twice throughout the rest of the scene.
Continuity mistake: When Buffy's friends come visit her at work, WIllow is playing with some straws in a styrofoam cup next to the register which disappears a few shots later.
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)
Continuity mistake: In the very last episode, Chosen, in the shot right before Spike's amulet sends out the blast through the roof, you can see an ubervamp just about to pin him against the wall and in the next shot he is standing in the middle of the area backing up toward the stairs and then he sends out the blast. There would never be enough time between the shots for Spike to break free and then go and stand in the middle of the floor.
Continuity mistake: When Xander's being threatened, the knife moves from under his chin to the side of his neck between shots.
Continuity mistake: In the kitchen scene Buffy takes the pizza out of the fridge and closes the door, but in the next shot the door is open and two shots later it's closed again.
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.