The Disease...
A 10-year-old boy walked up to a house of ill repute dragging a flattened frog on a string behind him. When the Madam answered his knock, he said, "I want to have sex with one of the women inside. I have the money." The Madam invited him inside and told him to pick any of the girls he liked. He said, "I heard a man talking about having to get a course of injections after making it with Amber. So that's the girl I want!"
The Madam, who was accustomed to strange requests from customers, told the little boy to go to the first room on the right. He headed down the hall, dragging the squashed frog behind him. Ten minutes later he came back, still dragging the frog, paid the Madam and headed out the door. The Madam stopped him and asked, "Why did you pick the only girl in the place with a disease?"
"If you must know," he said, "tonight when I get home, my parents are going out to a restaurant to eat, leaving me at home with my babysitter.
After they leave, my babysitter will have sex with me because she just happens to be very fond of little boys.
She will get the disease that I just caught. When Mum and Dad get back, Dad will take the babysitter home. On the way, he'll jump her bones and he'll catch the disease.
Then when Dad gets home from the babysitter's, he and Mum will go to bed and have sex and Mum will catch it.
In the morning when Dad goes to work, the Milkman will deliver the milk, have a quickie with Mum and catch the disease.
And he's the son-of-a-bitch who ran over my frog.