Visible crew/equipment: When the knights start advancing in the bottom right corner of the screen you can see a crew member wearing a red plaid shirt just standing there.
Visible crew/equipment: When Ben arrives in his car and discovers the Knights of Byzantium, the shadow of a camera on a crane can be seen in the bottom left corner of the screen as he pulls up.
Continuity mistake: The shape of the hole in the aluminium foil in the Winnebago's windshield changes shape several times throughout the course of the episode.
Continuity mistake: At the beginning of the episode when Glory gets hit by a truck, she lands on the roof of a car twice.
Revealing mistake: Watch the shot of Glory as she is hit by the truck at the beginning of the episode (easier to see in slow-mo/frame-by-frame). She isn't hit by the truck at all. It goes right past her. A simple optical illusion used in filmmaking for decades.
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.