David Letterman had a running bit on his TV show. He did it maybe four times, as far as I recall. It was a totally loopy concept, and I don't have a clue how they came up with it, who said in a meeting, "Hey, you could what would be really funny...?". But it was wonderful.
Dave would be talking at his desk, when all of a sudden Tony Randall would rush in with Mandy Patinkin. I don't want to say what happens, if you've never seen it, but this video embedded below is the first time it took place. All four were wonderful, whenever they did it, but this was the best. And I was lucky to see it take place "live," when I didn't have a clue that anything special was about to happen.
What's so good about this first one is that the audience didn't have the slightest idea what was going on either, of course, or what would occur. And so, at first, you can hear them tittering and giggling in ridicule. Because I knew something about old songs and recognized the verse, I could see where they were going with the thing, I got excited because I knew they were going to be amazed. (I don't want to say how I knew, but remember, as an idiot savant, this is not only my field of idiocy, but also...well, I'd seen Manny Patinkin in concert.)
Anyway, I watched both the performance and audience's reaction with interest. And if you ever want to see an example of someone grabbing an audience ready to mock you and then knocking them for a loop, this is it. After this performance, the audience was still always a bit wary when they'd do the bit again, but they were prepared. This time, though, this was the first, and they didn't have an idea what was coming, or what was about to him them.
You will now see way I'd been looking for this for 10-15 years. I don't like to oversell things. Don't worry, I'm not...