I can't believe I am even going to type this, but we call them a pee-pee and raisins. That is all DH's fault, he started that when DS was little and it has stuck ever since.
I just don't like how a 4 year old saying penis or vagina sounds, I don't know call me old fashioned, but pee pee sounds so much more innocent. I didn't get a vagina until I got my period.