Answer:
When one does not know what it is, then it is something; but when one knows what it is, then it is nothing.
Snow White was friendly with seven of them
Hands she has but does not hold, teeth she has but does not bite, feet she has but they are cold, eyes she has but without sight. Who is she?
It breathes fire in fairy-tales
What has to be broken before you can use it?
I always have to work with something in my eye. What am I?