I haven't thought about this in a LONG time, but many years ago, a couple of friends of mine would do a fake "reunion" cabaret act that they called,
The Sound of Music Man of La Mancha. In their "act," they would talk about how this was the first time that they had gotten together since they broke up years ago. What was really funny was that it was almost totally improvised! They would talk about their "act" and just go musically where their ramblings led them. They mainly did songs from the three shows, but not exclusively. And they'd also ask a member of the audience to come up and sing with them, but unbeknownst to the rest of the audience, that person was actually part of the show and totally in on it. It was hysterical!