When Charlie and an elf show Santa a new Santa suit towards the end of the film, the elf says Santa won't have to worry about fireplaces because the suit is flame retardant. Flame retardant means the material slows the flame down, but it doesn't necessarily keep something from catching on fire whereas flame resistant means it won't catch on fire. If the suit is flame retardant, Santa would have to be very careful going down a chimney with a burning fire, not worry-free.
When Scott Calvin is wearing the Santa suit in the early part of the film, the coat has a strip of white fur down the front. However later, when he gets arrested, the coat has two fur pom-poms down the front. And after he is released and comes back to the house, there is only one fur pom-pom on the front of the jacket.
While Charlie and his mom are saying good-bye on Christmas Eve, Scott is shown placing a cookbook on the counter. The shot switches back to Charlie and his mom. When the shot goes back to Scott, he is placing the cookbook on the counter again.
When Laura drops Charlie off at Scott's and he hugs her goodbye, he puts his hands on her shoulders. It then cuts to a close-up and his hands are clasped behind her neck. In the next shot his hands are on her shoulders again.
During the Santa Claus lineup at the police station, the Santas are instructed to turn to their right. But when the camera cuts back to Laura, the reflection on the glass shows the Santas all still facing front.
The scene where Scott and Charlie pull into the Denny's parking lot a sign that says "The Beer Store" can be seen. "The Beer Store" is where people only in Ontario buy beer by the case. This film is supposed to take place in Illinois.
If watched with closed captioning, Judy's voice comes from Scott's hat asking if he's OK while he's getting arrested. The caption shows Charlie's name instead of Judy's. This has been corrected in later releases.
When Charlie is telling his father about Neil's opinion on Santa Claus, Scott says that Neil is not a doctor, he is a psychiatrist. By definition a psychiatrist is a licensed medical doctor, who has not only earned a medical degree (MD), but has further specialized in the field of psychiatry. Scott knows this, but simply does not take Neil's profession seriously.
When Scott/Santa is arrested, he leaves Charlie and the reindeer waiting on the roof of the Miller house. When the E.L.F.S. squad comes to the house, they find Charlie alone. The reindeer and sleigh have disappeared with no explanation whatsoever.
Towards the end of the movie, when Scott Calvin has fully become Santa, he begins to make his rounds during the following Christmas. Legend has it that Santa only comes in the middle of the night after children are asleep, with references made alluding to this early in the movie. However, at the time Santa is arrested, he is shown delivering presents in what appears to be early to mid evening, with adults and children milling around the streets, still dressed and not in pajamas, and a fair amount of traffic on the streets.
Judy mentions to Santa (Scott Calvin) when he first visits the North Pole that she is 'seeing someone in wrapping', however, none of the presents that are pulled out of Santa's sack are wrapped, which begs the question - what is the wrapping department doing? Are they understaffed? Or did Judy, with full knowledge that at the time know that Santa had no understanding of the structure of the North Pole workplace, just lie to give him the brushoff?
Near the end of the film, as the SWAT team surrounds the house, you can see one team member slip near the front steps and the snow "buckles" revealing itself to be a blanket and not real, or even fake, snow flakes.
During Scott Calvin's first year as Santa, he visits Sarah, the little girl. She is clearly missing her two front teeth. She wants him to drink the milk but he says he is lactose intolerant. The next year she leaves him soy milk, and when she speaks she is still missing her two front teeth.
The very first time Scott and Charlie go to the North Pole, there is a shot of a female elf in a reindeer stall. She climbs up a step-stool, awaiting the reindeer's appearance so she can groom him. When the girl moves, a part of her left arm disappears, revealing the edge of the CGI special effects.
When the SWAT team pulls up to the house at the very end there is snow everywhere and it is obviously winter (Dec 24th). However, there is a maple tree in the front yard that clearly is in full summer foliage.
During Scott's first visit to the North Pole, when Bernard is explaining the consequences of Scott choosing not to believe in Santa, David Krumholtz's real curly hair is seen peeking out of his cap, behind the fake braids.