A pregnant woman boards a bus. After taking a seat, she notices a man smiling at her. She feels self-conscious and changes her seat, but he seems even more amused.
She moves a third time, and he starts to giggle. On her fourth move, he bursts out laughing.
They both get off the bus at the next stop. The pregnant woman is furious and demands an explanation. "What exactly is so damn funny?"
"I'm sorry, ma'am," replies the giggling man. "But I couldn't help noticing you're pregnant, and when you first sat down, you sat under an advertisement which read 'Coming Soon: The Gold Dust Twins.' Then you sat under an ad that read 'Sloan's Liniments Remove Swelling.' Then you moved under a deodorant advertisement which read 'William's Stick Did the Trick.' And I just couldn't hold it in any longer when you moved a fourth time and sat under a tire advertisement which read 'Dunlop Rubber Would Have Prevented This Accident.'"