The Spirit of Christmas
South Park Wiki; Wikipedia

I should say, I wasn't really sure whether to put this in my movies section, my TV section, or my web section. The first of these shorts was made in 1992, the second in 1995. They are what led to the 1997 TV series South Park. I don't think they ever aired on TV, but at least the second one became popular online before the series started. I didn't see the first one until 2013, when I decided to review both shorts. And I don't remember if I ever saw the second one before then, but if I did, it was probably within a few years after the series started.

Jesus vs. Frosty (3:52)
IMDb; TV.com; YouTube

There are some kids making a snowman. One of them says not to put a magic hat on his head, because it will come to life and kill them, but the others do it anyway. And the snowman comes to life (a la Frosty the Snowman), and immediately kills one. (The victim was named Kenny, but he looked like Cartman.) So the others try to find someone to save them from the snowman, and are ultimately rescued by baby Jesus. Um... I dunno what to say. It's reasonably amusing, but I doubt I'd have found it all that memorable, if the TV series had never happened. (Nor is it likely I ever would have seen it, if not for that.)

Jesus vs. Santa (5:12)
IMDb; YouTube

This one more closely resembles the series and the characters (it clearly includes Stan, Kyle, Cartman, and Kenny). Jesus (adult, this time) descends to Earth, seeking retribution against Santa for defiling the spirit of Christmas. Jesus and Santa get into a fight, which causes numerous incidental deaths (including Kenny, of course). Eventually they both ask the remaining boys to help them, and the kids have to try to decide who to help... but they end up getting some good advice from figure skater Brian Boitano. I don't wanna say any more about the plot. I definitely liked it more than the original short, though it's still something I'm not sure I would have found greatly memorable if not for the series. So, I'm glad the series exists, for its own sake as well as for the sake of making these shorts more memorable (and for making me aware of their existence in the first place).