Which One's the “Smart” Friend? Show Your Work.

Girl #1: I am just not a fan of the Jonas Brothers.
Girl #2: I don't know, the one with cancer is pretty cute.
Girl #1: What? I don't think any of them have cancer…
Girl #2: Yeah, the youngest one.
Girl #1: He doesn't have cancer, he has diabetes.
Girl #2: Oh, right! Because if he had cancer, he wouldn't have all that hair.

–Washington Square Park