I was thinking of all my Atari stuff last night and while I was brushing my teeth, I remembered when I was a kid and we had space invaders playing almost every waking hour, I remembered being able to double shoot, unlike the standard one shot from your guy at a time until it exited the top of the screen. As kids, we were able to do two shots. We figured it out by taking the console, turning it on with no cart in it, then inserting the cart, then turning off the console, and instantly returning the power back on and pressing the reset lever immediately as well. Once someone pressed game select the double shoot was lost, but you could reset all day long without losing the double shoot. Now, I didnt have the Atari Space Invaders, we had the Sears Tele-games version, I doubt there is a difference besides the label, but who knows.
I would be extremely shocked if this easter egg was not known on this forum, but I though I would share it after not finding any mention of double shoot in a search.
Kevin