>>328233What...
You seriously don't know the history?
Well, episode 1 was an animation error, or an animator joking, history will never know, after that, 4chan picked up on it, and eventually, as the brony community grew, Hasbro itself took notice, and Faust requested that every episode not yet aired should have her eyes "derped", thus, episode 15 and forward has Derpy as we know her.