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: He had larangitis and because of the shooting specifications they had to have him shoot the scene with a bad throat, they then re-recorded his lines and dubbed them. At various points during the scene and indeed the episode you can see him touch his throat or rub it.