Doing this without any major spoilers, so it's safe to continue reading! But if you haven't seen it yet, 'The Guardians of the Galaxy' Holiday Special is so good! Set aside 45 minutes, and enjoy!
Very early on we get to hear an original "Christmas" song called "I Don’t Know What Christmas Is (But Christmastime is Here)" from the alien band Bzermikitokolok and the Knowheremen, made up of Kortolbookalia, Sliyavastojoo, and Phloko. This lively rock number, aside from really not knowing what Christmas is, is hilarious and incredible!
We get a second song at the end of the film called "Here It Is Christmastime" - it's much more accurate to the holiday and, once again, incredible!
Whenever I hear a "fake" band in movies that is actually good, I always look up to see if they actually exist. And Bzermikitokolok and the Knowheremen do! But as the Old 97's.
But why Old 97's? They're director James Gunn's favorite band! James Gunn and lead singer, Rhett Miller, wrote "I Don’t Know What Christmas Is (But Christmastime is Here)" together! James Gunn also made the decision to have the band play the band - so what you see is the actual band in alien makeup!