When Naruto and Sasuke come to a final clash, all doesn't go as planned. Waking up without knowing where they were or how they got there, they decide to team up (Sasuke begrudgingly), they knew even for ponies they were small, they had been reduced to children again. Well it could be worse. Plenty of ponies wanted to 'help them'.
Well, they had good news at least.

They still had their ninja abilities, and that's always a plus.

"Look, all I am saying is despite all that power you're still children." Celestia frowned down at the two colts. Naruto waved his hoof.

"Never had parents, not gonna start now." Naruto grouched, Sasuke nodded, he had only one set of parents and they were dead.