Since the creation of the Elements themselves, the bearers of Harmony have never found true happiness. After seeing so many generations of unfulfilled ponies, Princess Celestia decides to do something about it.
What happens when the Reds and Blues finally get Church out of the Epsilon unit? Caboose decides he wants a turn in the unit, of course! What happens next? Well let's just say he always did say he wanted a pony, now he has a world full of them.