Quote from Joey in The One with the Ultimate Fighting Competition
Ross: So, Chandler, from now on, don't give your boss a chance to get you. Just don't turn your back to him. Joey: Or you could teach him a lesson, you know? What you could do is rub something that smells really bad on your butt, right? Then, when he goes to smack you, his hand will smell. Now, what could you rub on your butt that would smell bad?