Most of my readers have already heard this, but I'll relay the story here for posterity.  Earlier this week I was changing Devin's diaper; we were preparing to go for an outing of some sort.  Out of the blue, Devin looks at me and says, "Thanks for my penis, Dad."  The boy is 2½ years old.  I simply said, "You're welcome," and left it at that.  I'm afraid it starts earlier each generation...