Revealing mistake: You can see Buddy and Finch's stunt doubles in the ice skating scene. And when they are showing a close up of them you can tell that they are not really ice skating, but just doing the ice skating movement.
Continuity mistake: When Fred gets to the North Pole and the Security elves take him down. Fred comes up and the snow on his face change between shots.
Continuity mistake: When Dr. Sawyer is giving Kris the exam, during the part where Kris is doing the physical coordination test, we see Kris from Sawyer's point of view, and Sawyer is drumming his fingers. When the shot switches to Kris's, he is fingering his eyebrow. When it switches back, fingers drumming. Finally, when it switches back again, his hands are neatly folded in front of him.
Factual error: Trudie and her family are released from jail because David, being the victim of kidnapping, decided not to press charges. That's not how things work. It's not up to the victim to decide whether or not to press charges. It's up to the prosecutor to decide or not to press charges.
Continuity mistake: When Frosty gets off the train because Karen gets sick, from the magician's view it appears the train is slowing down and is very close to Frosty, but when the shot goes back to the magician, the train appears to be going much faster and is much further away.
Continuity mistake: In court, the camera shows Susan to judge her reaction to the lawyer talking, and she is sitting upright in her seat. It then changes to Dori, who is sitting right next to Susan. If you look in the bottom left hand corner however, you'll see that Susan is no longer sitting upright, and is instead leaning on Dori. There would be no time however for Susan to lean on her mother in the time the camera takes to move to another shot.
Continuity mistake: In the scene when Justin's father is coming out of the shed dressed as Santa Claus (the second time), the clock next to Justin reads 12:00. When he hears the "Ho Ho Ho" and gets up out of bed to go to his window, the clock says 11:56. (01:15:40)
Visible crew/equipment: A boom mic is visible at the top of the screen in one of the alternate endings where a mortician comes to get the body of Billy from the coroner.
Continuity mistake: When Kermit is in the park looking at his plaque he wipes off all the snow and reads it. In the next shot of him walking to a nearby bench the plaque is covered again but it is not snowing heavily enough to have been covered so fast.
Factual error: When Tom shocks Angela with a stun gun, she gets knocked out. That's impossible. Stun guns don't knock you out. Stun guns don't cause unconsciousness.
Factual error: There would not be that many leaves still on trees in December in Grand Rapids, Michigan. The snow looks very fake and sprayed on in some shots.
Revealing mistake: Toward the end, after Ricky decapitates the old Mother Superior, a young nun assumes she is alive and taps her shoulder. Mother Superior's head falls off and to the floor. There is no blood whatsoever. The old woman had just been decapitated moments earlier, and there isn't even a drop of blood, not even on the white part of her nun outfit at the neck.
Continuity mistake: In the scene where Richie is running away from the gaurds he dives over the platform and knocks over the statue with his foot, but when the other gaurds go to jump over it, the statue reapears.
Continuity mistake: While Bill waits for his brothers in the car, he looks toward the store and watches his brothers inside. The first shot of Bill's perspective of looking at the store, there is a reggae black man walking by. Then it switches back to Bill's face, then again at the store and the man walks by the window a second time in the same direction. When Bill gets out of the car and crosses the street the black man walks by a third time.
Factual error: There seem to be modern "Walk" and "Don't Walk" signs at each intersection. This film is supposed to take place in 1952. Also it is mentioned there are "Stereophonic" consoles in the motel rooms. Probably would not find those until at best the late 50s.
Revealing mistake: When Krampus walks toward Max after he yells at him to give him his family back, wires are controlling Krampus' arm. (01:24:30)
Continuity mistake: After the dogcatcher, Mr. Cluge, takes Puppy Paws to the dog pound, he unfastens the dog's collar and hangs it on a peg on the wall. The next time the collar is shown, it is fastened again.
Visible crew/equipment: Just before Johnathan Taylor Thomas climbs into the fake Santa's sleigh to sleep for the night, he is talking to Santa and playing with his hand. On his lower chest is the shadow of the camera (since the light is coming from behind the camera), which disappears in the following angle.
Factual error: The family supposedly left Ex-Yugoslavia (what part isn't made clear exactly) "because of the war", but the only conflict still going on there in 1999 (when the family is still there in the opening scene) was the NATO bombing of targets in Serbia in order to get the Serbs to lay off Kosovo, and that was long over by Christmas of that year.