Continuity mistake: Before and after Scott enters and exits the chimney pipe, the background shows the roof of the house with very little snow and the roof shingles exposed. The overhead shot showing Scott and Charlie leaving in the sleigh shows the same roof covered in snow.
Continuity mistake: While Bernard is explaining the "Santa Clause" to Scott Calvin, an elf dressed as a pirate behind Bernard exits the scene twice.
Other mistake: When Santa falls off Scott Calvin's roof, he slides in a straight trajectory that lines up just off center of the front door, meaning Santa should have fallen smack down on the snowless concrete walkway, not a few feet over onto the snow-covered lawn.
Continuity mistake: After Charlie gives the snow globe to Scott, the view of the back of Scott's head shows his hair and scarf, but the front view of Scott shows his winter cap all the way down to his scarf, which would cover his hair seen from the rear.
Continuity mistake: The articulating magnifying glass Bernard uses to read the "Santa Clause" off the card to Scott, the magnifying glass changes height between quick scene shots.
Continuity mistake: In the scene of Bernard telling Scott he is the new Santa by reading the card with the articulated magnifying glass, in one shot Scott and Bernard are in front of it, then suddenly it is between them.
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.
Revealing mistake: When the original Santa falls off the roof, the path he slides is already visible before he falls, especially in the point of view shot.
Visible crew/equipment: Near the beginning right when we see Charlie in the back of the car, the camera shadow creeps onto the vehicle as its moving.
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: 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.