Telling him you are pregnant.
Have you seen previews for a new movie called Knocked Up? The plot involves an educated woman getting a promotion and while celebrating, gets involved with some one-night stand bozo. 8 weeks later, she calls the guy up to tell him she is pregnant. The rest of the story deals with having the child and getting to know each other. When I saw the trailer, it reminded me of an old George Carlin joke.