End Of Days - S7-E21
Revealing mistake: When Buffy finds Faith and the Potentials in the sewers she throws an Ubervamp across the room. When we see the Ubervamp from behind you can also see the actor's blue boxer shorts sticking out of the Ubervamp costume.
Continuity mistake: Towards the end, when Buffy stops the arrow, when she first grabs it her hand drops down to Cassie's mouth level, and her arm's bent at the elbow. When we cut to another angle it's now held at arm's length and at about eye level.
Continuity mistake: Towards the end of the episode, when Buffy lands on the school bus she's wearing pointed toe pink shoes, but in the next shot where she's jumping off the bus roof, she's wearing brown Timberlake boots. (00:39:11 - 00:39:40)
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.