You Bet Your Wife
An old couple celebrates their 50th wedding anniversary in a honeymoon suite. All night long, the bellboy hears laughing and clapping sounds from their room.
The next morning, he asks the old man how he can do it all night at his age.
The husband replies, "First, I remove my clothes. Then, I lie down on the bed face up. Then, my wife removes her clothes and lifts up my penis with one hand, and we make a bet. If it falls to left when she lets go, I win; if it falls to right, she wins."
The bell boy asks, "Well, what if it doesn't fall?"
"Then we both win," says the old man.