This is really adorable, and probably one of the best Derpy/Ditzy pics I've seen on DA. You make her real adorable, while also capturing her "silly" side nicely here. The pinkness on her cheeks, and the way you do eyes are also quite cute. I also like your small details like how her hair/mane is blowing in the wind, and the feather coming off her wing.
Also I like how you referenced 2 famous fanons here of "Derpy loving muffins," and "Derpy being a postal carrier/Mail mare." Hehe
Your ponies are damn beautiful and adorable, your unique style just adds something special to them. I really hope you will draw Pony Princesses one day, Rachael (and by princesses I mean Celestia, not overrated Luna).
I am in love with the way you draw wings. Keeping a somewhat simple approach to it, you make the feathers so beautifully! And her eyes...they're so gorgeous. I can't get enough of those eyes! I don't know why, but I am in love with the messanger bag hanging on her hoof. It's such an adorable wonderful addition, and the detail of the bottom of her hoof is so great. <3
It makes me sad, I downloaded the episode with Derpy a few days ago. The voiceover for her voice is terrible. It just makes me saaaaad. </3