I thought the Dick Shawn thing sounded like an urban legend, but according to Snopes, it's mostly true. The only difference in their version is that he fell (because of a heart attack) and hit his head during a performance. And the crowd did think it was a joke.
I heard it the other way back when it happened. I'd seen Shawn do this particular show twice - it was hilarious. Guess the account I heard was not quite accurate, but close.