Twilight Sparkle awakes to find that her horn has disappeared! She is now forced to live the life of a earth pony, until she finds a cure for what has happened to her. The problem is that an earth pony cannot do magic, which means that Celestia's prized student can't be an earth pony! And Twilight is an earth pony now! Dun dun dunnnnn...

Although she may not be able to do magic, being an earth pony may appease somepony else.