A brony who goes by Dyrilby on Youtube, along with a friend, made a parody/original song called Equestrian Idiot. It's a parody, of course, of American Idiot by Green Day. As I said yesterday, everything is better when it's ponified. Give it a listen!
From what Dyrilby told us, he's planning to make an album. Not sure if it will be all parodies like this one, but he wanted to promote his stuff before he releases the album.
Thanks for sharing your parody, Dyrilby!