When Scott and Jack Frost travel back to Christmas Eve twelve years earlier, the former Santa vanishes immediately after landing on the ground. In the original film, he remained a solid body long enough for Scott to search his clothing and find the card.
In the first movie in 1994, Scott Calvin puts on the suit with a sash, and in the third movie when Jack Frost and Scott Calvin go back to twelve years earlier, Jack Frost puts on the suit with a belt.
When Santa and Jack go back for the second time, as they are watching Scott put on the Santa suit. Scott did not put on the suit on top of his house, it was the next house after they took of in the sled.
Just before Santa walks up to Lucy to ask her to hug Jack Frost he has her snow globe in his hand. After he asks her to do it, that is when she hands him the snow globe.
When the characters of Neil and Laura Miller unfreeze, Laura's zipper is undone on her pants. If you watch closely, as she unfreezes, her hands move in front of her pants and when she moves them again you can clearly see her pants are unzipped and then zipped again in the next frame.
When the toy-making machinery is going haywire, one of the elves tells Santa that the springs for the pogo sticks melted and presents him with the wooden body of a pogo stick (sans spring). Any metal that a spring would be made from would have a much higher melting point than wood would combust at. It would be impossible for a fire to be hot enough to melt metal springs while leaving wood intact.
After giving Lucy her gift, Santa says that's 1 down, 2.6 billion to go. At the time of the film's production, there were only about 1.8 billion children in the world, and the previous films established that Santa does not deliver to children who do not celebrate Christmas.
When Scott, Carol and her parents go in Santa's Workshop, you can see Elizabeth (Carol) checking that she's "on her mark".
When the elves are learning stress relief exercises from Neil, if you look to the upper right of the screen, you can see 5 elves that aren't wearing shoes.
When Scott receives the "Tree-Topper" Ann Margaret looks down to check that she's "on her mark".
Laura and Neal can be seen moving after they are frozen.
When Scott and Jack Frost fall through time and land in Scott's old yard, the crash mat they land on can be seen moving beneath the fake snow.
In The Santa Clause 2 Scott learns that he has to get married by Christmas Eve or he won't be Santa anymore. When Jack Frost is Santa Claus he doesn't have a wife.
When the old Santa falls off the roof, he says, "Ho, ho, uh-oh." He did not say this in the original movie.
When Lucy makes her way to the lobby to the Hall of Snow Globes during the musical show, the audio description on the DVD incorrectly refers to her as Laura (her mother's name).
When Lucy catches Jack Frost having Santa's snow globe, after she says, "I'm going for help," Jack says, "I wouldn't do that," but his mouth is not moving.
When Scott is making a distraction, he says, "Well, this show stinks." But his mouth is saying, "Well, this show sucks."
When Santa and the Sandman are visiting Sylvia and Bud, you can see a "Poly Blanket" (used to represent snow on flat surfaces, such as on a roof) in the tree behind Santa.
Santa has to perform the pass-code to operate the revolving door to the Hall of Snow Globes, whether entering or exiting it. Therefore, Jack Frost could not have exited the Hall without knowing the code.
The introduction of the Escape Clause in this film creates an error in the first one, where Scott asks Bernard what happens if he doesn't want to be Santa and Bernard effectively implies that becoming Santa is irrevocable. Bernard could simply have told him about the Escape Clause and his life could've then gone back to normal.
Lucy said that Scott gave Charlie the magic snow globe, when it was Bernard who gave it to him in the first movie.
The instant that the oven flares up, Bud rushes in with a fire extinguisher already strapped to his back and ready to use. There's no way he could've been prepared like that unless he knew it was going to happen.
Lucy watches Scott perform the combination with the Red Deer vending machine, even though he told her not to look.
There are three vending machines (North Pole Icy Bits, Red Deer energy drinks, and Elfsburg Choco Treats) in the vestibule of the entrance to the Hall Of The Snow Globes, but Lucy looks uncertainly around at all three machines, so obviously Scott neglected to tell Lucy which machine to use. He would never have neglected to tell her this important information, given his knowledge of how vital it was that Lucy succeed.
Scott tells Cupid that, "At this altitude, you might want to consider an under-diaper," referring to the cold climate for a man in a toga. Altitude refers to elevation, not position on the globe. He meant latitude, which refers to how far north or south a position is in relation to the Earth's equator.