One day a little boy and his mother were walking through a zoo. They came upon a zebra exhibit where two zebras were having sex.
The little boy asked his mother, "Mommy, what are they doing?"
His mother replied, "They're making cake."
After the zoo they went to the park. As they were walking they passed a couple having sex on a bench.
Once again the little boy asked, "Mommy, what are they doing?"
His mother responded, "They're making cake."
They went home.
The next morning the little boy walked into the kitchen and asked his mother, "Mommy, were you and Daddy making cake last night?"
She said, "Yes, why?"
The little boy replied, "I licked the icing off the couch."