Ha ha, I did that too, then I got scared when I saw what was actually inside!
BTW I also had a Skidoodle, which came out around 1980, which was about the same thing except it drew on a circle that you could rotate, and the control was a joystick-like thing. It worked the same way; I cleared the screen to see inside it too.
Cant find any web articles or pics right now, but has anyone seen that guy that does etch-a-sketch protrates for like thousands of dollars, then he takes the etch-a-sketch apart and somehow makes it permanant.
wait, it may be this guy http://www.gvetchedintime.com/