Continuity mistake: When Nora is driving down the road with Fromeyer at her window, he sticks his hands on the glass. Nora raises the window "catching his fingers". When looking through the windshield, you can see that the window is 3/4 of the way up, but when it cuts to the outside, it is just under the edge.
Continuity mistake: When the scouts are trying to sell a Christmas tree to Luther and Nora, there is a wreath on the front door. They can't make the sale and go to their truck parked across the street. They tell some neighbors that the Kranks would not buy a tree. As they all look across the street at the house, the wreath has vanished. When Luther leaves for work the next morning, the wreath has returned.
Continuity mistake: When the daughter's boyfriend first enters the house to meet Tim Allen and Jamie Lee Curtis, his hair is covered in snow. Shortly after, the snow is gone but then reappears in another shot during the same scene.
Continuity mistake: When the police are driving Blair and her boyfriend, it is snowing. In the shot from inside the police car the windshield wipers are on . The very next shot shows the police car driving down the street and the windshield is clear and the wipers are off.
Audio problem: Towards the end during the party we see a guy playing some sort of small pipe instrument. First of all, the timing of the moving of his lips on the instrument doesn't match the pipes heard in the music. Secondly, the lower notes that are heard in the music are heard when his mouth is at the shorter end of the pipe, which would realistically result in high-pitch sounds.
Continuity mistake: When the carolers are outside singing, Luther and Nora are inside hiding. When they cut to Nora, you can see out of the window- there's nothing there. When she leans back up from getting her yarn, the head caroler is there with some others behind her. In the next shot, they are back in place in the choir. Even if they were right outside the window in the first place, there is no way they could reposition themselves that fast.
Audio problem: When the carolers come to sing for the Kranks, it is professional-quality singing. Then the neighbors join and you can hear that more people are singing, and the quality of the singing is realistically worse(the neighbors can't sing well.) After a few shots of the carolers AND the neighbors singing, the sound goes back to just the carolers singing, though you still see the neighbors singing on screen.
Continuity mistake: Luther and Spike are removing expensive ornaments from the neighbor's Christmas tree so the tree can be moved to the Kranks' living room. Luther is behind the tree, opposite the window. In the very next shot, when a neighbor with binoculars looks to see what is going on, Luther is now on the side of the tree.
Other mistake: The local newspaper prints a photo of the Kranks' house along with a story about their refusal to put up lights and decorations. The story says that their street, Hemlock Street, finished 6th in the Gazette's decorating contest. But the name of the newspaper is the Journal, not the Gazette.
Factual error: When Mrs. Krank tries to snatch the Christmas ham in the parking lot of the grocery store, you can see trees with green foliage in the distance. Chicago never has green foliage on trees in the month of December.