Continuity mistake: In the season one episode 'I Will Remember You' when Buffy and Angel are talking in the sewer Buffy's hair goes from being just a few strands over her shoulder to having a whole side over it, and back again. (00:11:05)
Visible crew/equipment: When Angel kneels down to the fridge a camera lens is visible in the top left. (00:15:21)
Continuity mistake: When Angel and Buffy are sitting down talking about their kiss, Buffy picks up a coffee mug and holds it with both her hands. But in a wide shot shortly afterwards, she is no longer holding the mug and it has moved further down the table.
Answer: Due to his epiphany, Angel basically had the 'true darkness' he worked so hard to reattain ripped away from him, like his soul was after sleeping with Buffy.