I actually really liked the original design, with the eye patch that hides the derped eye. It let you know that GENERAL derpy was different than regular derpy because GENERAL derp was a HARD mother fuckin pony.
Ain't nopony gonna mess with general derpy, else they gonna get derped. Ya herd?
They're MMDs: Muffins of Mass Destruction. Entrusted to the only General powerful to guard what they love. Anypony who gets their hooves on those.........will have enough power to level Equestria. So if they get stolen, it's on whoever said Derpy doesn't guard them. Enjoy.
I think of Derpy as a well-meaning and educated mare whose eyes are a result of an accident that robbed her of normal eyes. She wanted to be a daycare worker(hence the bubble cutie mark. Kids love bubbles.) but the accident killed that dream. She's not stupid. She just likes muffins.