I'll start off with Family Ties "Miracle in Columbus" where the character Michelle Davies wears a fancy green dress with lace trim and white tights to the bog standard local mall, simply because she's the episode's spotlight kid. Who'd dress like that to go to the mall Santa?!
https://i.imgur.com/HGwoTwH.png

A Christmas miracle occurs, conveniently within the last 3 minutes.

Bonus points if no one knows how it happened, leaving the viewers to realize it was Santa Claus.

The "A Christmas Carol" and "It's a Wonderful Life" cliches.