A fitzy is the name of a term to describe an act mostly practiced on small boys.
To fitzy someone, the best location is a middle school bathroom. Find a small boy who pulls his pants down to his ankles when he urinates in a urinal, and kick him square in the nuts.
Matt: Dude yesterday I pulled a fitzy on this middle-school kid real good, he screamed like a little girl!
Joseph: Dude you're a jerk!
Matt: Whatever dude...