|RUUUUUUN! IT’S BEHIND YOU!|
Seriously, I didn’t even know this existed. Castle Creator is a game on the hub’s website where you can place ponies in different places in different scenes. How is this relevant? Because they updated it with Derpy.
Those folks over on EqD mentioned something about her image in the flash being called Derpy.swf, so I guess that’s the canon name now? I’m cool with that. I have no idea who took the time to find that out but the guy who originally found it and informed them is Whatshisgame.