This thread is awesome! I guess I missed it the first time around.
A book that my parents bought for me and my brother as little kids (all about being born) described sex in the following manner: (i read it about 50,000 times as a kid, i was a little pervert)
"One day when your mother and father were feeling very loving, your fathers penis became hard and slid inside your mother's vagina."
I always envisioned it as somethign they'd do like, on his way out the door to work, mom would hand dad his lunch, kiss him on the cheek, and have his penis poke her... and then when he came home it'd belike, "Honey I'm pregnant..." heheheheheheh.