"The Santa Clause" (1994)
You know the phrase "If you want a job done right, you have to do it yourself?" Well, that totally backfires for Scott Calvin (Tim Allen). After he and his son startle Santa on Christmas Eve, he stumbles off the roof and vanishes, leaving behind his sleigh of reindeer and gifts. Trying to make up for a disastrous night, Scott puts on the Santa suit and finishes the job of delivering presents. The sleigh returns him to the North Pole where he learns that, due to a "clause" in a contract, he has inadvertently accepted the job of Santa Claus.
Soon, the divorced businessman gains a shocking amount of weight, grows a beard, and develops a boisterous laugh. Despite his best efforts to live a normal life, he learns to become Santa and, along the way, a better father. It's heartwarming, hilarious, and yes, perhaps a little creepy to watch as an adult.