This is because of this post:
and now because of this episode!:
Addendum: I know Derpy still isn't show canon, but neither is Ditzy. Personally I think Derpy fits her better, because of the derp eyes, but anyway...
Lulz she's canon now!
Ready, aim, FIRE THE CANON CANNON!
Sorry, I couldn't help myself. Hasbro has been calling her Derpy for quite some time now, Mrs. Faust has called her Derpy in art and word, and now they officially do it for their official fan page.
I've always like the name Derpy. People say it's offensive, but run around calling somebody "Ditzy" and see how appreciative they are of that too. No matter how you look at it she's stuck with a name that is not the nicest, but she definitely has derped eyes. In any case, this is of course not a picture of Derpy, but rather her as a cannon. I figured it would be a nice idea because homophones (you know, words that sound alike).