Well, there are a few modern examples of plays with variable endings where the audience chooses. Shear Madness, for example, or the Dickens murder mystery where he never finished the story... I can't think of the name off the top of my head. The Mystery of Edwin Drood? Something like that.

But the reason I'm doing this research is because my theater company is doing a 'choose your own adventure' type play. It may be an utter disaster, it may be hilarious, it may be both... it's hard to say at this juncture.

And I hadn't heard that story about Steve Jackson, that's great!