Revealing mistake: When the elves are tying up the police officer at the station, they do so in a really quick manner. The film here is obviously sped up. You can tell this by the fact that the children playing the elves are breathing really fast.
Audio problem: When the cops stop the random Santa on the street thinking that he's Calvin, he says, "It's not even my suit! It's a rental!" But his lips are completely out of sync.
Continuity mistake: After Scott makes his first delivery at the first house he is being lowered by the toy sack into the sleigh on Charlie's right, but the next shot shows Scott lowering into the sleigh on Charlie's left.
Audio problem: When the elf special forces are about to take off and the female elf does a somersault, the sound that is created when they touch their wrist console can be heard over the sounds of the jet pack take off sounds. No one is even touching their wrists during the scene. (01:19:27)
Other mistake: A Federal Express driver delivers hundreds of boxes to Scott Calvin. They contain the names of all the children in the world. Scott opens a box and picks up the top page and begins reading the names. The second page in the box is identical.
Continuity mistake: After Santa falls in Scott's garden, before he vanishes he has some snow on the suit, but a few moments later the snow is gone.
Continuity mistake: When Charlie is hugging his Mom goodbye on Christmas Eve, his hands go from being wrapped around her back, clasped around her neck, then to her back again.
Audio problem: Outside the Miller's house the detective who was interrogating Scott is now shouting at the house with a bullhorn. When the detective lowers the bullhorn, his voice sounds like it is still being amplified.
Continuity mistake: In the first house visited by Scott as Santa, the amount of snow on the top of the chimney changes from shot to shot.
Chosen answer: Even though Charlie did not want to stay with his Dad for Christmas Eve, he did want to stay at home with a family member, fragmented as it was. Eating Christmas Eve dinner at a Denny's restaurant was not his idea of a Christmas dinner at home with family.