Wow! It thought it to be very hard to define a background pony with no real screen time- finding something that makes a cosplay so obviously Derpy seemed hard. But you've done it perfectly! Amazing cosplay!
I really wish I was born with blonde hair..it'd make it easier to cosplay many characters...(cause I could dye it what color I wanted) and do cosplays like this and Applejack >.< but nope, I'm a ginger. lol
I love ponies. Just not a fan of Derpy Hooves. Those google eyes kind of give me the willies. But everyone else seems to love her and I like that your cosplay picture has Derpy looking through love letters or fan mail. Like I said, It's very sweet.