The Wet Willy:
Usually performed on a sleeping or otherwise unsuspecting person, the perpetrator of a wet willy wets his or her finger with saliva and inserts it into the ear of the victim.
My Dad came up to visit this weekend.
My Dad likes to nap.
My Daughter likes to mess with people.
Grandpa + Nap + Daughter = Wet Willy
Ladies and Gentlemen... Class is in session.