Say what you want Brion but Aaron Neville's rendition of Silent Night is fucking priceless. It's comedic brilliance!
Besides, plenty of cool songs have been made about christmas like, "Christmas at the Zoo" by the Flaming Lips, "Christmas in Prison" by John Prine", "Happy Christmas (War is Over)" by John Lennon
Yes, I am aware that Celine Dion did a cover of that one and yes I was in pain throughout the whole thing.
As far as covers, the Motown Christmas covers are awesome, The Ronettes doing Frosty the Snowman, fucking mint!