Rainbow Dash has a secret. A secret she has kept since she was a little filly. If it gets out, it could be the end of her reputation, the end of her carrier, and even the end of her friendships.
And what's worse, is that a resent shortage threatens to expose her.
(Inspired by Don Ko and the image to my left.)
(It should also be noted that this story is non-canon both in relation to the actual show and in relation to my personal Head-canon, which is what I usually like to write about.)