***** Derpy appears with intentionally crossed eyes in Feeling Pinkie Keen; 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 Raindrops, who are hovering next to a movers' truck. *****
WRT 'bubble wrap', her cutie mark wasn't from Faust. As she mentioned here on dA when asked about Derpy: "Background ponies have no name, and their butt symbols are picked at random."
The job as mailmare wasn't (isn't?) canon, either:
Ah, sorry, I was just trying to clarify her backstory and history, esp. WRT bubbles/bubblewrap / mailmare being non-canon. Since she appeared in S1E1, Faust was the voice of canon for her initially.
In terms of where the fandom has taken her, esp. WRT Dinky, I find her flaws endearing, and outside of Dashie's treatment of her in The Last Roundup (well, and Winter Wrap-Up), I think it's good to see that Ponyville society remain inclusive.
Certainly it can be argued that she lacks nuance as-is and may be a Christmas special martyr as Snowblind puts it, but I think Faust's take on it, while she is fully clear that this is the fandom's character, she can provide the Harpo Marks slapstick-y character.
To reiterate, though, my initial response was based on the incorrect assumption that you were speaking of Derpy's canon background, so I apologize.