Goldenrusset (The Director for MLP FiM) has sent a tweet off to Weird Al asking him for a guest appearance! So far he hasn't responded yet, but it's still neat to see people from the FiM team actively posting around on the internet. I can only imagine how crazy a Weird Al Pinkie Pie episode would be!
Anyway you can find his Twitter below, and the exact quote:
@alyankovic mlp/yankovic make a perfect pair! Ever consider doing a guest spot on the show? (I'm the director and a huge AL fan)
Weird Al's Twitter