Actually, Lauren Faust originally designed Pinkie Pie to be a Pegasus Pony, but in the end ended up giving her wings to Fluttershy. I don't recall why she had her wings transferred, but in the original concept sketches of Pinkie Pie, she had wings. That kinda explains why Fluttershy has such a strange ability for a pegasus pony (communicating with animals)
i know, i believe her name was originally supposed to be Surprise, too. but from what i’ve heard, they’re somewhat different ponies.