My Little Pony: Friendship is Magic - Unlimited Power'll Do That To A Girl

Then she let her wings fall, and the light in her eyes faded, and she laughed with a sudden clear laugh, and lo! she was shrunken: a slender alicorn-mare whose gentle voice was soft and sad.
'I pass the test,' she said. 'I will diminish, and go back to Ponyville, and remain Twilight Sparkle.'
--J.R.R. Trotkin, The Fillyship of the Elements

Teenager?