[markem]

That little bastard Little Johnny was passing his parents bedroom in the middle of the night in search of a glass of water. Hearing a lot of moaning and thumping, he peeks in and catches his parents in the act.
Before his Dad can even react, little Johnny exclaims, "Oh boy! Horsey ride. Daddy can I ride on your back?"
Daddy, relieved that Johnny was not asking more uncomfortable questions and seeing the opportunity not to break his stride, agrees.
Johnny hops on and daddy starts going to town. Pretty soon his mummy starts moaning and gasping and Johnny cries out, "Hang on tight, Daddy. This is the part where me and the milkman usually gets bucked off!"