Children can be very inquisitive.

The other day Avi asked me the difference between a sperm and an Afro. After a deep breath I thought I did well, despite the giggles of her elder sisters, to explain that a PERM is a chemical treatment for hair...etc, etc, etc.
Her little sister took it all in,and tapped me on the arm.

"Mummy,"she asked, "Have you ever had a sperm on your hair?"