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).
Buffy The Vampire Slayer (1997)
2 deliberate mistakes in season 2
Continuity mistake: When Buffy is talking to Riley, she puts the scarf on her head, on his hand. He talks to her and says "Maybe I am the bad guy," and in the next frame her scarf is back on her head again, then off again in the next frame. (00:24:20)
[After saving Giles from a vampire.]
Spike: Awww, poor Watcher. Did your life flash before your eyes? Cup of tea, cup of tea, almost-got-shagged, cup of tea?
Band Candy - S3-E6
Trivia: The accent that Giles uses as his teenage self is Anthony Head's natural accent.
Question: At the last moment before leaving for good, Angel pauses to tell Buffy "I don't like him" [Riley], to which she replies with a large smile "Thank you." Why does she take this comment surprisingly well? From an ex boyfriend to her new boyfriend? It's not like it sounds like a friendly warning of any sort, nor a joke given the tense situation between the two guys in the episode. And the smile on Buffy's face does not make her response look ironic either, more like loving/caring. Is that a cross over reference to another dialogue in the Angel series?
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.