Poor Frog

A little boy walks into a brothel dragging a dead frog behind him. He asks for a prostitute with herpes. The lady says "Ok, whatever turns you on" and takes him upstairs. On his way out the lady says "why did you want one with herpes?" the boy says "Well, if I shag her then I get herpes, I go home and shag the babysitter and she gets herpes, my dad comes home and shags the babysitter and he gets herpes, my mum comes home and shags my dad and she gets herpes, the milkman comes round and shags my mum - and THAT'S THE BASTARD THAT KILLED MY FROG!"

That's a good one.