Continuity mistake: When the awful cousin Charlotte hands Gwen the slice of unbirthday cake, she does it with her right hand, left hand, right hand. (00:04:20)
Continuity mistake: The layout of the two slices of pizza on the tray and the position of Tyler's fork on his plate differ after Matt reaches the table. The slices of pizza are touching, then spread apart like a "V." Tyler's fork moves from being diagonally across his plate with tines facing him to being situated near the edge of the plate with tines facing Jessica. (00:13:19)
Continuity mistake: After stabbing the bad guy at the beginning, Callahan for some reason pulls back and somehow dives past a door managing to drag in a grown woman who was all crouched down by the entrance. Wonky physics of it aside, the bad guy shoot at him, but shoots just a hole in the door frame. The hole appears to be CGI, and in fact when Callahan shoots back from the bedroom, the hole is gone. (00:01:35)