Previous working titles include "Buck-Ass" or "Kick-Plot". Originally called Buck-Ass but was changed because Kick-Flank is 20% cooler, and Kick-Plot doesn't make much sense outside of the pony community, so that's a no-go too.

Applejack is now the son of the leader of the Diamond Dogs. Go figure.

Rainbow Dash is Big Daddy because Big Daddy looks like Batman: https://www.youtube.com/watch?v=Sfu_Zn5zkX4

Video: My Little Pony: Friendship is Magic
Kick-Ass trailer

Audio: Kick-Ass trailer