Continuity mistake: When the reindeer gets into the house and runs around, it knocks over a TV set. All of the magazines that are on top of the set come crashing to the ground, including a TV Guide with "Get Ready For A Fabulous February" (or something like that) in big letters on the cover. Interesting since the movie is set around Christmas time.
Continuity mistake: When Jessica sits on Santa's lap in the department store, and asks for the real Santa's help to assist Prancer, she pulls down Santa's beard a bit. In one shot, the beard is definitely below his nose, after it is pulled. In another shot, the beard is right up under his nose. There are various shots where the beard is up one second and down the next.