Other mistake: If the dead characters all are continuously displaying how they died, Adam and Barbara should constantly look wet, but they don't.
Other mistake: When Satsuki enters the shot when she, Mei, and their father visit their mother in the hospital, Mei seems to be constantly staring up at their mother with her mouth gaping wide open.
Other mistake: When Jack stumbles into the wrong bedroom, he witnesses Mary's murder twice. Later, Mary reveals that she gets murdered only once every night.
Other mistake: Josh's birthday, according to the milk carton, is in the winter. But, some time after he celebrates his birthday at the Italian restaurant, he returns to his childhood neighborhood and it's fall (colored leaves, etc.). It can't be the following year because he's only gone for a total of a few weeks.
Other mistake: The two headed monster's heads are pretty big. Big enough to swallow a person whole. But when Val Kilmer jumps on one to impale it, the sword comes out of the bottom of the monster's head. For this to happen, the sword would have to be unbelievably large, larger than a man, which he would be unable to wield anyway.
Other mistake: When Eddie Valiant gets thrown out of the Ink and Paint Club, he is already starting to go through the air as the gorilla moves his hands to throw him. (00:21:20)
Other mistake: When Frank and the Ghost of Christmas Past are at the office Party where the younger Frank is still working, as they stand by the entrance door two women leaving move in closer to try and avoid bumping them - despite the fact that the Ghost said earlier they couldn't be seen or affect what's going on.
Other mistake: The 3rd movie takes place 5 years after the original, since Kristen is still in high school this one can't take place too long after that. How does Nancy's house get so run down in only 5 or 6 years?