Ds1 (almost 4yo) is really curious about the "baby in my tummy," and he loves it whenever I look at pictures of babies in utero (including US). So, the other day, I popped "In the Womb" into the dvd player. He loved it, although he was confused about the footage of sperm and eggs at the beginning.
I told him that the mama and daddy each make part of a baby (and what those parts are called), that the daddy gives his part (the sperm) to the mama, and the parts get together and make a baby. He seemed to understand.
"And Daddy likes making babies all the time!"
I could have died.
From the mouths of babes...