guy 1: "I was about to give this homeless guy some money, but then I heard a rattlesnake and ran away."
guy 2: "You idiot, that was just a detroit rattlesnake."
Telltale sign that you are pissing off your wife, girlfriend, and/or significant other. With legs crossed, the leg on top starts bouncing at an increased pace the more agitated the subject becomes (usually a lady).