Twilight Sparkle wakes up one morning, to find she's living with her family and is a filly again. She's not in Canterlot but in Ponyville though, and that's just the beginning of the changes. Like her new school, and the identity of the Headmare...
The Cutie Mark Crusaders will Discover the perks and the problems of being adults while they take care of an alicorn filly and her friends, but dont worry, they can handle it... Right?
When a new age spell is too powerful for Princess Twilight to handle, the Mane 6 find themselves as newborn foals again. Only this time they're all under the motherly guidance of Celestia and Luna.
Twilight has been fascinated with the new power she and her friends received; Rainbow Power, but as she continues to study it and attempt to tap into their newfound powers again, something... Odd happens.
Twilight accidentally turns her friends into foals - including her - and Pinkie has to take care of them all before they wreak havoc on SugarCube Corner.
After a magic accident, the Bearers of Harmony have been returned to a state in which they need somepony to look after them, Celestia assigns the job to an unorthodox, but loyal, guard.