I quite read the whole song and noticed the second verse: "A day or two ago, I thought I'd take a ride, And soon Miss Fanny Bright (or Rarity or whatever), Was seated by my side, The horse was lean and lank, Misfortune seemed his (her) lot, We got into a drifted bank, And then we got upsot ((poetic) Alternative form of upset. (I searched it))" Well, you ponies better be careful!
I am not gonna make it in time for christmas so I quit the idea but the concept was: Derpy as rudolph the derpy reindeer, Pinkie as a cupcake Santa, Spike as a very unhappy elf and the others standing watching with "huh???" expressions. Sorry :/