Dad was getting the kids ready for bed, brushing teeth and such...
Bubba: Dad what happened to your hair? (pointing to the back/top of Dad's head)
Dad: Sigh... Well, every time one of my kids screams, whines or cries about something for no reason at least 10 hairs fall out.
Bubba: Then what happened to G-Pa's hair?!
Dad: Well, that's another story...