Cats

Teacher: "If I gave you 2 cats and another 2 cats and another 2, how many would you have?" Johnny: "Seven." Teacher: "No, listen carefully... If I gave you two cats, and another two cats and another two, how many would you have?" Johnny: "Seven." Teacher: "Let me put it to you differently. If I gave you two apples, and another two apples and another two, how many would you have?" Johnny: "Six." Teacher: "Good. Now if I gave you two cats, and another two cats and another two, how many would you have?" Johnny: "Seven!" Teacher: "Johnny, where in the heck do you get seven from?!" Johnny: "Because I've already got a freaking cat!"