“Coitus interruptus by SWAT team. At last a form of birth control that was one hundred percent reliable.”

“The Hitchhiker's Guide is a hundred percent accurate. Reality, however, is not as reliable.”

“Fifty percent of something is better than than one hundred percent of nothing.”

“I'm telling you, if aliens landed on earth today and took a good hard look at why babies get born, they'd conclude that most people had children by accident, or because they drink too much on a certain night, or because birth control isn't one hundred percent, or for a thousand other reasons that really aren't very flattering.”

“He squinted at me. "What are you wearing? Is that some new form of birth control?”

“Serious reading is hardly a social activity and every halfway serious reader is perpetually subject to a form of coitus interruptus. Family members or friends who lack the desire, the courage, or the opportunity to burst in on you when there's some indication that you could be sexually entwined will seldom hesitate to interject themselves between you and a page, even though the act of reading is often as intimate and intense as a full-fledged carnal embrace. You must take steps to ensure your privacy.”