When you're a kid, few things amuse you more than a twisted Christmas song. Everybody remembers "Jingle bells, Batman smells." My personal favourite was "We three kings of Washington Square / Try to sell some cheap underwear / This elastic, it's fantastic, $3.99 a pair."
Anyway. This was probably the first one I heard in recorded form, and it wasn't even based on a pre-existing carol. "Weird Al" went to the trouble of penning an all-original (two, if you include "Christmas At Ground Zero," which I like less) Christmas song, about Santa going on a murderous rampage. He knew his audience.