My Little Pony is actually a pretty good show. It's actually cleverly written, as opposed to other shows of its type, with intelligently-written, likeable characters and clever pop culture references, my favorite being "Read It and Weep" with its rather involved Indiana Jones and Tomb Raider parody.
My own in-universe character would be a Nuckelavee, a race I created myself, decribed below,with grey skin, dark mane with blue-dyed tips, blue tattoos, and violet eyes.
Nuckelavee are a bipedal, equine species from the Osprey islands (a play on the Orkney islands, where the legend originates). They have an unfortunate reputation as criminals and other shady types, not helped by their rather frightening appearence, with translucent skin and slightly glowing eyes. However, one shouldn't judge a book by its cover, as they have a deeply-ingrained sense of honor and integrity, and have distinguised themselves as leading members of the Equestrian military.
I imagined them as being more humanoid than the other species, closer to a creature from Grimm, but that's just my take on it, seeing as the Nuckelavee in Orcadian legend is a human-horse hybrid.
Anyway, love the show.