"Waddling Like A Duck" joke
A couple of young medical students were standing on a street corner watching people as they passed and discussing any abnormalities with each other that they may have noticed in the passers-by. They would then attempt to make the proper diagnosis.
An old fellow left a bar and they noticed he was waddling like a duck as he slowly went down the street. The two students introduced themselves to the old man and told him that they disagreed with each other's diagnosis of his problem.
One of the students said, "My friend says you have a hernia, and I think you have a bad case of hemorrhoids. Which of us is right?"
The old man replied, "Well, guys, I thought it was a fart, so it looks like we're all wrong!"
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