Continuity mistake: In the season 4 episode "Doomed," during the fight at the Hellmouth, Willow throws the sack of bones to Spike, who catches them and looks startled. In the very next shot of Buffy fighting one of the demons, Spike can be seen in the upper left corner of the screen, with empty hands, quite calmly watching the fight. (00:36:35)
Visible crew/equipment: At the end when the gang leave the high school, stage lights are reflected in the broken glass of the double doors that they exit through.
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.