General Computer Corp. (GCC) is famous (or infamous, depending on your view)
for programming Quantum and Food Fight for Atari. This was as a settlement
with Atari after producing the unauthorized "Super Missile Attack" hack of
Missile Command. The settlement actually called for them to make three games.
Nightmare was the third game, and it was never released. I'm pretty sure
someone out there in net-land owns one of these machines (I heard it
mentioned at CA Extreme) so if you have any information you'd like to
share, I'll be here patiently waiting for you...