The one about the botched vasectomy....

While doing a vasectomy, the doctor slipped and cut off one of the man's balls. To avoid a huge malpractice suit, he decided to replace the missing testicle with a pickled onion.

Several weeks later, the patient returned for a checkup. "How's your sex life?" asked the doctor.

"Pretty good," the man said, to the doctor's obvious relief. But then the patient added, "I've had some strange side effects that are causing serious problems."

"What's that?" the doctor asked anxiously.

"Well, every time I urinate, my eyes water."

"Hmm," said the doctor, thoughtfully.

"That's not all," continued the patient. "When my wife gives me a blowjob, she gets heartburn."

"Hmm," said the doctor, as his face reddened.

"It gets worse, Doc. Now, every time I pass a hamburger stand....I get a hard-on!"