Supposedly making out for 20 minutes burns 400 calories.
Actually, 400 Kilocalories, but food companies thought it would be easier to denote those things we burn as calories, so what the hell. Apparently metric prefixes are fucking scary.
Chad: "Hey Lisa want to burn 400 calories?"
Lisa: "Sure Chad, but I'm not taking off my pants...yet."
{ 20 minutes later }
Chad: "Wanna burn 400 more."
Lisa: "Let's go for 2000. Take off your pants."
tiny, microscopic creatures who live in your closet who sew up your close each night to make them smaller. They do this out of jealousy and hatred for the human race for not recognizing them as existent.