Squidball

Question: How do you get a large audience, seated in a theater, to play cooperatively?
Answer: Squidball

I quote: "Squidball is played with several...large (approx. 4ft in diameter), helium-filled weather balloons in retroreflective jackets -- these are the input devices for the game. By throwing, batting and bouncing the balloons throughout the playing field (which, in this case, was approximately 400x200x40 cubic ft), the audience plays to eliminate the on-screen targets, which are represented on a giant 40-foot video screen that also displays scoring and timers. As a result of this unusual motion capture application, the audience sees the balloons move across the two-dimensional video projection screen as they simultaneously interact with them in the 3-D space. Winning the game inspires and requires collective cooperation among the entire audience."

It's kinda brilliant, you know, taking that balloon Thing they do at events like Jethro Tull concerts and making that the interface between audience and game. That Balloon Thing is probably the only play-if-you-want-to, nobody-hurt, not-really-interrupting-anything-important, genuinely pointless, large audience game in circulation. And it's fun, too.