Continuity mistake: After Perry and Harry leave the lake with the girl in the trunk, the headrests are missing from the front seats, but when the shot cuts to them arriving at Harry's hotel, they reappear.
Continuity mistake: When Harry and Perry were on a rooftop after finding out the identity of the girl in the lake, Harry was talking non-stop and Perry puts up his left hand to Harry's mouth to stop Harry talking. When the scene cuts, we see that Perry has his right hand up instead of his left.
Continuity mistake: When Gay Perry returns to toss Harry's stuff out of his car window, he drops Harry's jacket right outside the car. But when we cut to a wide shot a moment later, Harry's jacket is several feet away, as if it had been thrown.
Continuity mistake: In the scene where Harry is lying in the backseat because his finger broke back off, he is lying down so his head is behind the driver's seat. When he wakes back up, he is lying the other way with his head on the passenger side.