Where did Adam_148 get THAT? I think you're thinking of the Master Sword, which can only be USED by the pure of heart.

I think they look like pajamas. If you're going to wear a tunic, you usually wear leggings, not pants. But why does it really matter?
I've seen more than one picture of Aryll with skulls on her dress. Why skulls? In the game, her dress has flowers.
That's the kidn of pajamas-or-clothes detail I don't really care about.