This is actually from 2010. They're having a 2011 performance, but it's in the East Coast. Funny. They sing at the end so stick around. :DCute gif on the bottom.
Original songs are after the break if you haven't heard them yet. :)
Last Christmas By WHAM! (The name of the band) :P
Taylor Swift also sings it and it isn't bad
All I want for Christmas By Mariah Carey
This song is more well known(At least I hear it more) :D
You guessed it: Wonderful Christmas Time