He's been disguised all his life, hiding away from the general Pony population. But one filly makes him break his shell and teaches him that life isn't all about hiding away.
A simple challenge for the sake of a contest: a prize to be claim if possible; a crossover experiment in media res so to speak. Failing that, a short story with low expectations and higher inquiries based on its contents in question nevertheless...
He's been disguised all his life, hiding away from the general Pony population. But one filly makes him break his shell and teaches him that life isn't all about hiding away.
Caught in a rainstorm again, Derpy trudges off toward home. But along the way, she finds somepony down on her luck as well, somepony who very much reminds Derpy of her own childhood. It was a good day.