I wrote a bit about the ET pre-show previously. I copied it below from Day 2 to save you the trouble of clicking on it...I know...soooo considerate. Here is the Etch-A-Sketch in action. Here is how we erase a giant Etch-A-Sketch.
My buddy John Verostek joined me for the Electronic Theater tonight. We were handed a paddle with a green side and a red side when we entered the theater. When you walked to your seat, you could see on the screen the layout of the theater with green and red lights representing every person holding up their paddle with the green/red side facing the screen. You could find your dot on the screen and flip your paddle to make your light turn red or green. We did some fun interactive games with this gimmick. The best was the giant Etch-A-Sketch projected on the screen. The audience was divided in half. One side controlled up/down by displaying red/green. The other half controlled left/right by displaying red/green. If the audience was split 50/50, then nothing would happen. Mostly green would move up, mostly red would move down. Same goes for the audience with the left/right controls. We were given the task to trace the outline of some shapes: a square, a triangle, a circle, and (of course) a teapot. And how do you clear an enormous Etch-A-Sketch? You shake it, of course! We all shook our paddles in unison and the screen would clear. It was a lot of fun...even though they had some problems registering our paddle information in the section I was sitting in.
The first game we played was bouncing a beach ball around. When the ball came to your area, you were supposed to flip the color of the paddle. Here is the video of it in action. We were still learning how it works at this point...so I think you'll only see one bounce and lots of "buzzing" (meaning you didn't bounce it in time).
Another game was pong with a dog as a ball. The goal was to hit the dog past the other teams "fence" so it would fight their cats. I did this game at a previous SIGGRAPH...I want to say New Orleans in 2000. Here is the video.