|Screenshot of Season 1, Episode 1|
The little grey pegasus first appeared in the background of the first episode, and due to an animation error had eyes pointing in two different directions. Fans noticed the filly, and assigned her characteristics based upon her goofy appearance, christening her "Derpy Hooves" and assigning her ditzy qualities. A few people questioned whether equating a wall-eyed appearance with ditziness or stupidity was offensive; a few more pointed out that the term "derp" might be a slur against people with disabilities. However, despite these minor rumblings, the pony became a fan favorite.
The animators noticed, and began to give a few nods to fans with the placement of Derpy in humourous background scenes. For example, in Feeling Pinkie Keen (Season 1, Episode 15, and controversial in its own right), the pegasus is shown to be behind a classic cartoon gag.
"...when Twilight spies on Pinkie Pie, a series of objects falls on her head: a flower pot, an anvil, a cart of hay and finally a piano. A camera pan reveals that the items were dropped by Derpy and her friend Raindrops, who are hovering next to a movers' truck."In season 2 these inclusions have become increasingly deliberate, culminating in
A lot of focus is now being given to the use of the term "derp" being offensive. On one hand pony t-shirt purveyor We Love Fine has dropped the name "Derpy" in their product descriptions. On the other is a petition to not change Derpy's name.
But it seems likely that the name is not the only cause of complaints. As was mentioned earlier, it might be considered offensive that a physical abnormality is combined with stupidity in this character. As well, the pony's voice might be of concern, though that's admittedly open to interpretation.
It's unclear what, if any, action Hasbro will be taking with regards to this controversy. No notable action has been taken on other complaints with the show (see: "Feeling Pinkie Keen", above; there have also been concerns of racism surrounding Zecora and the Buffalo from "Over a Barrel", which haven't stopped Zecora from being a returning character).