"Golf and Sex Joke" joke

So there are three golfers, (Bob, Max, and Ted) who are looking for a
fourth. Bob mentions that his friend George is a pretty good golfer, so
they decide to invite him for the following Saturday.
"Sure, I'd love to play," says George, "but I may be about ten minutes
late, so wait for me."
So Saturday rolls around. Bob, Max, and Ted arrive promptly at 9:00,
and find George already waiting for them. He plays right-handed, and
beats them all. Quite pleased with their new fourth, they ask him if
he'd like to play again the following Saturday.
"Yeah, sounds great," says George. "But I may be about ten minutes
late, so wait for me."
The following Saturday, again, all four golfers show up on time, but
this time George plays left-handed, and beats them all. As they're
getting ready to leave, George says:
"See you next Saturday. But I may be about ten minutes late, so wait
for me."
Every week, George is right on time, and plays great with whichever
hand he decides to use. And every week, he departs with the same
message.
After a couple months, Ted is pretty tired of this routine, so he
says, "Wait a minute, George. Every week you say you may be about ten
minutes late, but you're right on time. And you beat us either
left-handed or right-handed. What's the story?"
"Well," George says, "I'm kind of superstitious. When I get up in the
morning, I look at my wife. If she's sleeping on her left side, I play
left-handed. And if she's sleeping on her right side, I play
right-handed."
"So what do you do if she's sleeping on her back?" Bob asks.
"Then I'm about ten minutes late," George answers.
Pete Granger