When Finn was young and first learning to speak, we somehow began to identify his primary boypart as his ding ding.
The phrase seemed cute enough at the time--especially because Finn was actually able to say it himself--and I've never really understood the need for very young children to know the clinical names of their body parts. Piggies are adorably interchangable with toes; nobody really needs to know at that stage in the game that they have phalanges. (Plus, it's always a little strange and to hear a two year old scream out in the grocery store about her wagina.)
So, now that he's "four and a quarter," John and I decided that now may be the time to introduce the formal names of his anatomical bits and pieces so he's not left standing aghast and aflutter should the word penis be introduced on the playground. (Oh, you and I both know that day's coming. And soon.)
Finn's nightly bathtime was chosen as the easiest and most convenient place to open the discussion, and John stepped up to the parenting plate with characteristic aplomb.
J: "So, Finney, did you know your ding ding is also called your penis?"
F, lying flat in the bathtub with his ears and head semi-submerged underwater: "Did you say PANTS?"
J, laughing: "No, Finn. I said penis."
F: "Is that Spanish, or something?"
* This, by the way, cracked me up something fierce.