Earlier this month Amy Keating Rogers, one of the writers for MLP:FiM, released a small batch of information on cut material from some of the episodes. Apparently AJ had more of a part in the MMMystery Express and some songs were cut from The Best Night ever! The information is a little old, but for those of who have not had the chance yet to see them, well, take a gander after the break!
Thanks to Whatshisgame for sending this in.
Click the images for the original source.