“Royalty is no fun without royal subjects. Special to knight people.”
There are two ways to do this, but here is the easiest one:
Go to the area where they are having prom. Headbutt dame carrie, that's it.
Prom Goat can shoot out golden dust which when contacts people, it gives them a princess tiara.
Prom Goat is a goat with a princess tiara and a dress.