Once upon a time, there was a sperm named Stanley who lived inside a famous
movie actor. Stanley was a very healthy sperm. He'd do pushups, somersaults, 
and limber himself up all the time, while the other sperms just lazed around
doing nothing.

One day, one of the sperms questioned Stanley why he exercised all day.

Stanley explained, "Look pal, only one sperm gets a woman pregnant, and when
the right time comes, I'm gonna be that one sperm!"

A few days later, all the sperm could feel themselves getting hotter and 
hotter. They knew the big swim was imminent. Moments later, they're released
abruptly and, sure enough, Stanley was swimming far ahead of all the others.

Suddenly, Stanley stopped in his tracks, turned around, and began to swim
back with all his might. "Go back! Go back!" he hollered. "It's a blow job!"