Many games have secret messages hidden away, just waiting for the right combination of control movements to reveal them. There are three known 'Easter Eggs' in Williams games:
Robotron- three control combinations have to be performed. You can hold each combination as long as you like, but there can only be up to a quarter second between each combination.
This sequence reveals some text. Releasing the fire up stick returns you to game over mode.
Stargate- again, three control combinations are required, with the same timing restrictions.
This produces a page of text. Releasing move down resets the machine.
Sinistar- the exact sequence is unknown, but probably ends with inserting 3 quarters. I disassembled the code and found the routine. I set the NMI vector to this address, so I could jump here by shorting CPU pin 2 to ground. Here's the picture.
Williams Arcade Classics for Win95 has the steps hidden in a text file somewhere on the CD!
All the game ROM images have some ASCII text that isn't part of the game. Every game has multiple copyright messages, and many games have other text. Stargate's Easter Egg text, like Robotron's, is not plain ASCII, but there is ASCII text in Stargate that says nearly the same thing. Sinistar has one of the developer's names (Robert J. Mical) included.
