Fonzie

Fonzie, or too Fonzie.
Fonzie is when you jam your thumb into another persons anus, one of the two parties involved in the act yell Heeeeeyyyyyyy!

Dude 1- So I was banging this chick, and I stuck my thumb in her ass, and she yelled Heeeeeyyyyy, so I pulled it out.
Dude 2- Oh so you fonzied her!