Answer:
I can be as thin as a picture frame but my insides have many things you can see.
What goes up when rain comes down?
Casper was a friendly one and Demi Moore made a clay pot with one.
A king wears one on his head.
A prehistoric reptile that lives today and the inspiration for the name of a popular sports drink.
Those with eyes bigger than their stomach will definitely leave the restaurant with one of them. It is named after a house pet as well.