I loved today's episode. So now it's canon that Starlight Glimmer can magically at will turn herself into a foal and back into an adult mare. But she's grown enough to know when to undo the spell when it's making other ponies uncomfortable.I like to think that Starlight will occasionally change back into her cute filly self whenever she wants to have childhood fun again, but still with her adult mind. And remind everypony it's a magic spell so that they don't freak out and faint.