10. You have an iron stomach.
Jenny: What's going on? You don't look so hot!
Mike: I have a stomachache. I think I got some bad food at lunch today.
Jenny: Really? But we ate at the same place. How come my stomach is fine?
Mike: You have an iron stomach! My stomach, on the other hand, isn't as strong.
Jenny: So what should we do now?
Mike: I've got to find a restroom - and quick! I think I've got the royal runs.