She was at one point fully canonized by name in the show, but stirred up some controversy among the fandom after she was deemed offensive and ultimately had her name removed.
HistoryNot only had Derpy Hooves become the poster pony of the fandom, but her discovery was the origin of the "background pony fanon" trend. For example, Lyra, Bonbon, and Berry Punch have initially appeared in the series premiere, however, their names and fanon weren't established until months to come. Derpy was the first.
Origin and Name
The animators in the studio would normally give the background ponies a nickname just for the sake of making placement easier. Such names for this grey pegasus would include "Bubbles" or "Stoneface".
However, times had completely changed when a stillshot of the show was noticed by a few alert /co/mrades on 4chan's Comics and Cartoons board, which revealed an animation error that perceived the pony with a walleyed expression. Most of the community members of the young MLPG were quick to grab on to this opportunity for fanart. This was posted on October 25, 2010.
The users on 4chan then gave her the name of "Derpy Hooves". The term "derp" originated from a South Park episode and is now commonly used to describe one who is clumsy. However, definitions deeper in the dictionary may also associate the term "derp" with "ableism," an issue that would later bite back the fandom with relentless drama a year later.
Recurrence and Following
Likely due to the show's budget and the cost effective technique of "cloning" in Adobe Flash, Derpy had made multiple appearances in the show with underped eyes from episodes 1-14. At this point, Derpy still retained her state as a blank slate. Briefly in Episode 4, Applebuck Season, Derpy appears as one of the ponies to eat Applejack's "baked bads". During this brief camera-panning, the audible word "muffins" is heard, and is assumed to be spoken by Derpy. In "Winter Wrap-Up," a clumsy pony dubbed "Ditzy Doo" is blamed for falsely directing the southern birds.
Portrayal in Fanon
Her brief moments in the show were apparently all that /co/ needed to bring her into fanon character development. Not only is she portrayed as a wall-eyed pony, but due to her brief moments in the show, she is now depicted as a muffin lover. However, her depiction as a mailmare did not originate from the show. It traces back to a brief fanfiction excerpt called "Bright Eyes" published on November 14, 2010, which that name at the time was a variation of Derpy Hooves.
"I Emptied your Fridge" is a phrase that originated in a sketched comic from an MLPG thread, dating back to January 21, 2011. According to Sethisto on EqD, it was "probably the biggest pile of drawings at one time ever."  You can find the original artist of the comic drawn by Elosande in his DeviantArt gallery.
Eventually, the comic was redrawn and colorized by an artist by the name of Ace, which became the more widely viewed version of the famous comic.
Bubbles is another fanfic that goes into the backstory of Derpy Hooves, published on March 2011. It included a collection of tales of Derpy that led to an assumed downfall of her parents faith with her. The final scene includes her blowing bubbles by the tree, which acquires her the "bubble" cutie mark. It is assumed by the reader that she is abandoned by her parents.
Portrayal in Canon
Due to her lurking on 4chan at the time (she admits this later), Lauren Faust was quick to notice the fanart surrounding the Derpy Phenomenon and replied to the following DeviantArt Message.
|“||First off, let me say just how much I’ve been enjoying My Little Pony, Friendship is Magic. It’s clever, well conceived and EXTREMELY well written. But I was wondering if you could clarify something for me. You may or may not be aware that MLP FiM has a growing fanbase (helped along by YouTube), and fans being the way they are jump on some points of production and running wild with it. In the first episode, there is a grey pegasus with a blonde mane at Pinkie Pie’s party with loopy eyes. Fans have dubbed her “Derpy Hooves” and she’s blowing up. I’m coming to this party a little late, but I was curious as to whether or not this pony had a name or not and what her cutie-mark represented. Thanks for any help you can give in this and keep up the good work.||”|
|“||Ha! I lurk around a bit and I noticed the Derpy phenomenon. As far as I know, her wall eyed moment was an accident — or perhaps a layout artist entertaining him/herself. Who knows? Background ponies have no name, and their butt symbols are picked at random, so she can be Derpy if everyone likes. A later episode references a less-than-intelligent local pegasus named “Ditzy Doo” so maybe she can be her if we ever need to show her. But I would not want to step on everyone’s Derpy love.||”|
–Fyre-Flye (Lauren Faust), DeviantArt
The implementation of this clumsy personality then became canon in "Feeling Pinkie Keen" involving her clumsiness with packages, where she drops a flower pot, an anvil, and a piano on Twilight's head. This scene is the first time she appears with intentionally derped eyes, and is often considered the first time Derpy is recognized as the personality the fandom made her to be.
Starting from Feeling Pinkie Keen, the staff and animators began to use her "Where's Waldo" type cameo appearances 
In the Spring of 2011 following the Earthquakes in Japan, Lauren Faust herself participated in a charity auction herself by selling several of her "Pitch Bible" sketches. Metacritter, the winner of the auction, decided to put one of these sketches back up on eBay, of course, after asking for permission from Lauren Faust. She later posted this response.
|“||I’m offering 2 more drawings from the same batch of development sketches---- plus a brand new sketch. The first time I’ve ever drawn this character.||”|
–Fyre-Flye (Lauren Faust), Deviantart
The sketch of Derpy sold for $2151 USD.
Appearances in Season 2
In Season 2, she became more involved in the storyboard process, including a scene where she hoof-wrestles the mayor over the Smartypants plushie. It was mentioned by Lauren Faust that Derpy "would have a speaking role in Season 2" on her deviantart account in September 2011, however, many people hadn't took notice of it.
It wasn't until January 21, 2012 at the premiere of "The Last Roundup" did Derpy get her first official speaking role, which practically shook the whole fandom. She is seen striking herself with lightning shouting her first canon quote "I just don't know what went wrong!" which is now commonly associated with derpy amongst the fandom. Stats on Google Trends showed that her name was being thrown around faster than ever. The response was almost all positive, except for the few who weren't very fond of her voice, which suggested that her antics were offensive to the mentally handicapped.
Controversy over "Ableism"
Apparently, amongst the first people to take wind of the potential controversy was Derpy Hooves News, who foresaw that while they didn't take anything personally against it, they believed that it could provoke some drama sometime in the future. After some discussion in the air about this, on February 1, iTunes removed the episode with her speaking role, without any further explanation. Initially, this was perceived to be an an error among iTunes' part, seeing as they were notorious for misnumbering episodes. Equestria Daily, on that same day had acknowledged the iTunes removal  but dismissed it after a leaked email screenshot had claimed otherwise. EqD commented that "a supposed 'uprising' of angry anti-derpy people popped up." The screenshot was later removed as requested, however, saying "you'll have to take our word for this one." The events on the next day proved otherwise. On February 2, ChefSandy reported that "if you want a shirt with the word 'Derpy' on it, get on it right now. They're going away. DHN later confirmed that these specuations were true. Meanwhile, Equestria Daily dropped a petition link  asking to avoid this.
One of the loudest crusades of the "Anti-Derpy" drama was led by Yamino, who was later followed by 4chan when a petition asking to remove the wall-eyed pony started appearing on Tumblr.
The first community to oppose the "Anti-Derpy movement" was /co/'s MLPG. While this community usually discourages any form of raiding, their general distaste for the so-called "social Tumblr justice" is even more sour. Yamino later responded to this unexpected attention, explaining that she didn't have any semblance to the spreading petition on the "problematic elements with the character" [sic], but rather, was just "a high profile fan who has mentioned it a few times." A screenshot of her traffic showed that her garnered attention has given her over four thousand views in one day.
On February 6, Equestria Daily posted a Youtube message from an interview where Everfree Northwest's Markarian talked with one of Hasbro's Representatives about the future and stance with the brony community, which led much of the fandom to believe that Derpy was in good hands. Soon, the fandom calmed down.
"The Last RoundUp" changes
Meanwhile, the newly established Pony board on 4chan, /mlp/, was flooding with posts en masse of biblical proportions. This event would later be dubbed, "Derpygate," by its board's regulars, along with the rest of the fandom community. Their community, however, which wasn't as forgiving as /co/'s MLPG, lashed back at Yamino and the Anti-Derpy crowd for their doings.
On February 25, Kreoss, an animator of MLP:FiM and TopDraw posted a message on his DeviantArt account  assuring the community that Derpy will retain her derped eyes in the next season. As a side note, it turns out that he was lurking one of the streaming chatrooms aware of Derpy's speaking cameo, awaiting the inevitible flood.
Kreoss also asked the community to stop hounding Yamino, and said that "she had NOTHING to do with the sudden change. She expressed an opinion on Derpy. That is all. She did not ask me to do this or anyone on the staff." However, Yamino is still recognized by quite a few members (notably from 4chan) as an advocate to this infamous edit.
Later that day, a pony animation team that was really popular at the time, nomorethan9, posted a video called "Save Derpy" which essentially became the epicenter of the upcoming attempt to return Derpy to her original state. This short has received over a million views in the first nine months.The site, savederpy.com went online and received much attention from media outlets. The hashtag, #SaveDerpy began to spread in massive proportions in these turnings of events. In this same week, Derpy had reached #9 on the U.S. Top Trends on Twitter.
On March 2, Amy Keating Rogers responded to the changes in the episode, explaining that out of the 200 fan letters she received, only ten of them were actually complaints. She further defended the ableist claims stating that her son, Soren, is severely disabled, and she forbids the word "retarded" in her household.
Throughout the entirety of season 3 up until the finale, Derpy has not appeared anywhere. The absence of the wall-eyed has gone anything but unnoticed by the community, which enforces the possible rumor that she will no longer exist in Season 4. She is still visible in the intro of Season 3, but due to the incarnation of Twilight as an alicorn, the remaking of the intro is practically guaranteed.
Hard to believe this wouldn't have happened if it weren't for that trivial animation error in Season 1.
- ↑ http://www.determinismsucks.net/archive/co20771786.html#20774035
- ↑ http://www.derpyhoovesnews.com/origins/
- ↑ http://www.equestriadaily.com/2011/01/story-carrot-cake-storybook.html
- ↑ http://elosande.deviantart.com/gallery/?catpath=scraps#/d37tc7a
- ↑ http://mlpfanart.wikia.com/wiki/Bubbles
- ↑ http://fyre-flye.deviantart.com/journal/37155514/
- ↑ http://mlp.wikia.com/wiki/Derpy.
- ↑ http://fyre-flye.deviantart.com/journal/39270057/
- ↑ http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=280662542214
- ↑ http://www.youtube.com/watch?v=geTCP666Yf4
- ↑ http://derpyhoovesnews.com/derpy-hooves-mentally-handicapped-or-just-clumsy/
- ↑ http://www.equestriadaily.com/2012/01/addendum-to-derpy-hooves.html
- ↑ http://www.change.org/petitions/hasbro-studios-the-hub-return-derpy-s-scene-in-the-last-roundup-to-normal
- ↑ http://yamino.deviantart.com/journal/So-much-love-and-tolerance-in-the-air-right-now-283013711
- ↑ http://www.youtube.com/watch?v=nM-j1S4Ppr8
- ↑ http://web.archive.org/web/20120303011040/http://www.ponychan.net/chan/show/res/36223075.html
- ↑ http://www.derpyhoovesnews.com/derpygate/
- ↑ http://kreoss.deviantart.com/journal/Derpy-287023334
- ↑ http://www.youtube.com/watch?v=cg-_HeVNYOk
- ↑ http://www.savederpy.com/
- ↑ http://www.equestriadaily.com/2012/02/amy-keating-rogers-response-to-derpy.html