Little Billy and his frog

Little Billy is walking down the road dragging his flattened frog on a piece of string behind him.

He walks up to the local brothel and taps the door, when the madam answers, he says, 

“I want to have sex with your dirtiest girl who has lots of diseases; I have £500 to spend”.

The madam’s eyes light up and she says,

“That’ll be me then, but why do you want a disease?”

Little Billy says, 

“Tonight, after Mum and Dad leave, my babysitter will shag me because she likes cute little boys. Later when Dad runs her home he’ll shag her in the lay-by. When he comes home and goes to bed, Mum will want a good seeing to and tomorrow when Dad goes off to work, Mum will shag the milkman………

And he’s the bastard who ran my frog over!”