Continuity mistake: When Mabel holds the valentine card, she does it by the side (right heart) and the top (left heart). In close-up, she merely holds it by the bottom of the right heart. (00:19:10)
Continuity mistake: Chief Newby called the insane asylum, but couldn't get the information he needed. As he speaks with the mayor, Hanniger is listening with his cigar in his right hand, lowered to his hip. In a close-up, though, his cigar is in front of his chest. (00:16:10)
Continuity mistake: Hollis is holding a cigarette in his hand when he tells Happy that it's "a stupid legend," but in the reverse angle, the same hand is holding a bottle. (00:14:20)
Continuity mistake: Once he has been mocked by Howard, Happy the bartender leaves his yellow rag behind. Gretchen looks like she is about to push it away, but in the next cut, the rag has changed place and she hasn't touched it. (00:14:10)
Continuity mistake: After the flashback to the events of 20 years prior, the town prankster blows a raspberry at the bartender. The girls laugh with him, breaking their previous stance (they were both leaning their cheeks against their hands), but in the next shot, the short-haired blonde is still in the previous pose. (00:14:05)
Revealing mistake: When the boys are playing five finger fillet, notice that their hands on the table have skin colour and texture different from their actual knife-wielding hands. Hollis's actor is also doing the fakest back-and-forth motion ever. (00:10:50)
Continuity mistake: When the Mayor finds the human heart inside the box, the police chief next to him at the wheel has his pipe in his mouth, then he does not, then he does again and slowly removes it as if he noticed the heart just then for the first time - but he has already brought the car to a full stop in the previous shot. (00:10:15)
Continuity mistake: Quantity and position of fake blood on Howard change during the scene when he pranks the elders and then delivers the heart box. (00:08:00)
Continuity mistake: When the mayor asks Mabel to just concentrate on having a good time on Saturday, she is holding the box with her left hand underneath it in the wider angle, but under the tighter angle, you can see her palm on the side of the box. (00:07:50)
Revealing mistake: In the very first murder shown in the movie, there's a close-up of the victim's heart tattoo. Immaculate skin, nothing that stands out about her skin other than the ink. In the wider shot when she leans forward before being pushed back and impaled, you can already see there's some bulging under the tattoo where the pickaxe is designed to come out. (00:02:50)
