Continuity mistake: When Ricky is being inspected for metal by the two prison guards, he opens his shirt so to reveal his chest. His right nipple (or left from the viewer's POV) is exposed, but in a close-up shot of his chest, the nipple is suddenly covered by his shirt. (00:05:28)
Continuity mistake: When the red haired woman is undressing to enter the jacuzzi to kill the guy, her red dress is either on top of the white robe, or next to it, depending on the shot.
Continuity mistake: The little girl who was missing after falling off the cliff, suddenly shows up again after the evil woman is struck by lightning and is seen standing with the other children to react. But then she's gone again only to then show up with Santa.
Continuity mistake: Janet goes back and forth from needing to wear glasses to seeing perfectly fine.
Suggested correction: Janet wasn't real. She was a character in Jack's delirious dream. In Jack's dream, he was saying the things Janet was doing was written by Federman, and sometimes he controlled the scene. Not to mention the fact that some people only need glasses to see certain things and can see without them in other incidents or she was wearing contacts.
Continuity mistake: When Cynthia Rothrock acts as a bait for the maniac at the beginning of the movie, she is walking down the nice and brightly lit slums in black high heels. A fight ensues, and she kicks him around wearing black sneakers (after her triple roundhouse she strikes a pose in a wide shot and it's very noticeable). Her incompetent partner joins in late, and she walks out on him wearing high heels again. (00:01:55)
Continuity mistake: In the first meeting with the man with the hat, Ice puts one foot on the portable cooler, but the position of the foot on the floor changes when there's a cut. Even more obvious, when she steps in front of him, the tip of her red stilettos touch his feet, but at the cut their tips are distant, and she moves in with her right foot first, as opposed as before. (00:09:15)
Continuity mistake: When Jason and The Count duel, the cut on Jason's cheek is already there before The Count cuts him there. By that point, Jason was only cut on the shoulder.
Continuity mistake: David goes downstairs and finds out about his surprise birthday party. The tape recorder and the other objects on the table change position between shots around the ugliest cake ever. (00:05:25)
Continuity mistake: When Lena sees Julie's body in a trunk her right arm's sticking out. A shot of Lena then suddenly Julie's arm is folded over her body.
Continuity mistake: It wasn't snowing in the front of the house (e.g, when Ethan, Hallie, and Stephanie were going home; when the ambulance arrived; when anyone came in the front door), but it was snowing heavily in the rear of the house during scenes showing the Christmas tree. (01:18:24 - 01:20:42)
Continuity mistake: Cynthia walks alone to Joyce's house and also leaves by herself to clean the van. She speeds away from the house in order to clean the van in secret, but she somehow has her toddler son with her while she is cleaning the van. (00:46:45 - 00:52:16)