A father and his 6 year old son are walking home from school and the boy sees two dogs going at it. The son asks his dad, "what are they doing?". Dad replies "they're making puppies."

Later that evening, the boy wakes in the middle of the night and wanders into his parents bedroom. As he turns on the light, he sees mom and dad going at it. The boy asks his dad "what are you doing?" The dad replies "making babies son."

The boy replies "well roll mom over ... I'd rather have puppies."