Liam writes a letter, misspelling Santa as "Satan" and Jack Black appears to grant him three wishes to claim his soul. Yeah, a pretty thin three wishes cliche, wrapped in a holiday tale. Jack Black overtries at every turn to make this fun and, in fairness, without him this would be a complete waste of time.
If you're bored waiting for the turkey to finish cooking, you can watch this turkey. Better yet, just avoid it. Not funny, not heartwarming, not good.