Continuity mistake: In the scene where Santa is getting married, just after they kiss and Santa looks like Santa again, you can see in the bottom left hand corner Bernard and Curtis giving each other the thumbs up. In the very next shot, it repeats them doing this again only in a close up. (02:33:00)
Other mistake: The little girl elf pours Santa a mug of hot chocolate, but if you watch closely there is nothing in the mug when he drinks it.
Revealing mistake: In the beginning of the movie when Charlie is in the gym, the last can of spray paint he uses, just before the Principal catches him, appears to spray 'clear'.
Revealing mistake: At the end of the movie, watch closely as Santa comes to tell Lucy about how he is Santa. He comes through the chimney and shakes a little bit. Later, when he leaves, that very same shot is shown (with all the same movements), only in reverse.
Continuity mistake: When Charlie goes down the rope (in the beginning of the film) to spray paint the wall in the gym, the rope hangs tight from his point of view, but loose from his girlfriend's point of view.
Factual error: When Santa is shown the miniscule print on the 'Santa Clause' card (that he is supposed to be/get married) the Elf holds an enormous lens in front of it, to make it easier for Santa to read the print. From the distance Santa is standing at, from his point of view the card should appear upside down.
Audio problem: When Abby, an elf, is about to tell Santa that Charlie is on the naughty list, she says something about 'Brazilian cocoa beans'. As this line is heard, you can see that her mouth is moving completely differently from the words we hear.
Continuity mistake: In the scene where the clone Santa is sitting at his desk reading the book of rules, one of the elves gives him some cocoa and he sets his magnifying glass down. In the next shot, the magnifying glass isn't there, and in the next one it has magically reappeared.
Continuity mistake: Before Curtis announces, "The de-Santafication process has begun!", his arm is bent and his hand is holding on to the sleigh while standing a distance away (rear shot of him) but when he says the line his arm is by his side and standing much closer to the sleigh (frontal shot).