"Weirder things have happened." Not an unfamiliar phrase to hear spoken by the residents of Ponyville, the unofficial strangeness capital of Equestria. If something outlandish, peculiar, or just plain odd is going to go down, that quaint little village is a pretty safe bet as to where. The fact that it's also where the bearers of the Elements of Harmony call home means they're usually involved in one way or another.
When Pinkie finds an atypical coin in her path one morning, it sets off a chain of events that's, well, rather par for the course when you consider where we're talking about. In any case, what happens when the currency in question exchanges minds when changing hooves?