Harold and I had an Etch A Sketch that didn't work anymore. I have often wondered what kind of mechanism was inside that made those things go. So we took it out to the shop to see what we could figure out.
They are not really meant to be opened, so it took a lot of work to get it apart. Some of the pieces inside got misplaced while opening it, so we couldn't tell exactly how it works, but it is some sort of system of pulleys and wires that move the pointer around. The back of the Etch A Sketch says that the powder inside in non toxic, what they don't tell you is what a terrible mess the stuff makes if you let it out.