i remember hearing a fake audio clip about an episode like this :P

I’m honestly surprised that the show hasn’t done a body swap episode yet. It’s practically a stock cartoon plot at this point.
 
If they DO end up doing one, I hope they don’t have the voices actually swap. It’d be much funnier if the different actors used the same voice, but with the mannerisms and speech patterns of the characters they swapped with. Though you’d have to make sure that AJ and RD didn’t swap with each other, and that Pinkie Pie and Fluttershy didn’t swap with each other, because that would probably just get too confusing.
 
…Oh, god. Can you imagine Twilight talking like Pinkie Pie? Or AJ talking like Rarity?