Little Suzie and Cake Baking
One day, little Suzie and her mom are walking down a beach when they see a couple having sex. Little Suzie asks her mother, "What are they doing?" And her mother replies, "They're baking a cake" so that she doesn't have to explain sex to little Suzie.
Later that day, after mom has tucked little Suzie into bed, little Suzie's dad comes home. Mom and dad decide to have sex on the couch.
The next morning, little Suzie goes up to mom and asks, "Mommy, were you and daddy baking a cake last night?"
Mom replies, "Yes we were, Suzie. How did you know?" Suzie replies, "Cause I saw some icing on the couch."