The geek gene was hardwired into his DNA

Milo sees a guy on TV wearing nothing but a chainmail vest. “That can’t be very warm.”

Me: “No, but if someone hits him it’s really going to hurt their hands because they’d be hitting metal. And it won’t hurt him so much because the metal will absorb the blow.”

Milo: “Yeah. That’s why it doesn’t hurt Superman when people hit him—because he’s the Man of Steel.”