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!