Here's a holiday staple that's still enjoyable, even if it's a bit silly overall. Tim Allen is a divorced dad who accidentally falls into the Santa "clause" when the real guy falls off his roof on Christmas Eve. He then finds himself at the North Pole (a high tech lab in this one with immortal kids as elves instead of old people) and literally morphing into St. Nick as the next Christmas fast approaches. Sure it's silly, but it still has some funny lines from Allen and Judge Reinhold and a very cool North Pole set-up (one of my favorites in the movies, actually). It works, and for that reason it's still a fun re-watch every year at this time, especially for kids. Stay away from the sequels though- they're almost bad enough to destroy the original, trust me.
Original 1994 Trailer: