Yes, this has turned out to be an incomplete list; but these were all of the Easter eggs that we knew about in '98. We include the article anyway, for the sake of completion (and as a possibly entertaining, whimsical return to more naive but very enthusiastic days). There were good intentions behind it, after all! CF 6/3/11
The reason these can all fit into one article is that without all of the tricks that deal with frying (turning the 2600's power off and on really fast) and other such error-evocations, which were unintentional on the parts of the programmers (separating them from genuine secrets as far as I'm concerned), they can be made quite compact and still adequately explanatory. So here we go -- plug in the VCS and get ready for a treasure hunt!
The Easter Eggs...
Adventure -- The very first secret message, this is also the most involving coding-wise, the niftiest and the most rewarding. Warren Robinett had an extra bit of memory left over once the game was finished (5% of the allotted 4k of ROM), so he decided to add a whole extra room with his signature in it to get even with Atari's policy of not giving programmers individual credit for their games.
Select game variation 2 or 3. It helps to get the bat out of the way for this excursion, but it's not necessary; in game 2, you can grab him right away, bring him southeast into the catacombs, force him to grab the gold key, bring him back to the gold castle and force him to unlock it, dropping him inside and trapping him for the duration of the game if he's flying diagonally upwards, straight up, straight left or straight right when you drop him.
Anyway, get inside the black castle with the bridge. Exit the bare anteroom, traveling north. Exit the screen above that, the first dark maze screen, through the top but bearing west. Once you're in the second, higher maze screen, work your way into the screen to the west, and then into the screen south of that one.
Have the bridge below you. Just to the south and east of the center, there's a little chamber that can't be accessed except by walking south over the bridge. Once you're in that little box, walk along the tiny eastern wall, simultaneously pushing that way, until you hear the sound indicating that you've picked something up. As you work your way back out of the castle, you'll notice that you've grabbed a dot. Robinett has said that it's only one pixel in size, deliberately seeming unimportant. But we know better!
The dot will be invisible in all of the rooms except the dark mazes, but you can see it by sticking it into a wall (just don't drop it there!). It can be dropped and re-taken, acting like all of the other objects except that the bat won't steal it and the magnet won't attract it. Bring it to the room that's one screen south and one east of the gold castle. Drop it anywhere in there. Bring enough objects into the room to make the eastern boundary line blink (the chalice often negates the line's new transparency, for some reason), and then walk through the line. There it is -- the biggest chunk of memory ever not referred-to in an instruction manual!
There's a lot of other neat secret stuff in this game. You can use the bridge to walk partway through a northern or southern wall and see what room would be adjacent to the current one if there were a doorway. Once you win, you can hit the SELECT switch as the victory "song" is playing to hear it at half-pitch and half-tempo. Once you're back to the selection screen, push down on the joystick and see your hero appear in this numbered room!
Bump 'n Jump -- Whether it's intentional or not, being merciful in this M-Network game and not wiping anyone out results in an extra life and 50,000 bonus points after any course. SELECT also acts as a "Continue" switch!
Carnival -- Steve Kitchen, brother of Garry (2600 Donkey Kong, 2600 Pressure Cooker, C-64 GameMaker and others), made this home adaptation for Coleco. His message, an alternating two phrases featuring his signature, appears in place of the score instead of the first and second values that you can attain once you've flipped it. But this goes by really quickly, so try the easier way:
Turn on the 2600 with the fire button held down. You'll notice a little dot in the top row of targets. Shoot it before it scrolls off the screen, since you only get once chance. The game locks up, but Steve's egg alternates indefinitely.
Combat -- Here's one of the few mentionable "probably bugs" in this list: Hold down the fire button as you release the RESET switch. Now you can fire all the way across the screen.
Communist Mutants From Space -- This Starpath game contains Steven H. Landrum's initials. All you have to do is hold down the fire button as the game's loading from the SuperCharger and then look at the high score.
Defender -- Get to wave 25 (i.e. the wave after the number 24 is displayed) in any variation except the Mutants-only games. Rescue a Humanoid, but don't deposit him; fly to the height at which you start out (the 25th raster line, incidentally) and then look at the aliens. You can find the right height by watching the baddies blink briefly into different guises as you adjust your ship vertically. Once you're stationary on the correct raster line, they remain transformed; the initials stand for Bob Polaro.
Desert Falcon -- Swim in the northern part of any lake while charged with a Superpower to see the programmer's initials.
Dragonstomper -- Yet another Steven H. Landrum creation for the SuperCharger. While the axe is onscreen, enter the command "Use shield" to see Landrum's initials.
E.T. -- Howard Scott Warshaw's eggs were almost as involving as Warren Robinett's invention. Choose the non-enemy variation to make this easy. Pick up seven Reese's Pieces but don't fall into any wells (you want to avoid the flower for now). Call Elliot and give him the pieces. Now find all three phone parts, still avoiding the flower (use the question mark icons). Now you want to find the flower. Get near it and try to make it bloom, and you'll see a character from another Warshaw game (look quickly!).
Get rescued, winning this round. Press the button to start your second adventure, and repeat the above procedure. Another non-E.T. character will pop out of the flower.
The third time, Warshaw's initials will replace the energy reading at the bottom. The number near his initials in any of his egged games denotes the sequence in which he wrote the games.
Fathom -- Rob Fulop was already notorious for egging games before he left Atari to join Imagic (see the Missile Command section). Here, he doesn't sign his initials; he displays Imagic's address! The catch: You have to rescue the mermaid seven times.
G.I. Joe -- Finding the currently untraceable initials in this unique Parker Brothers battle involves hitting the fifteenth Cobra eight times while playing the two-player, cooperative variation at its easiest level of difficulty.
Kaboom -- Scoring 10,000 changes the Mad Bomber's facial expression. He's shocked! Har. Serves him right.
Missile Command -- Start a game on variation 13 and let all of your cities get demolished (as painful as this is to just sit and watch). Rob Fulop's initials will pop up from the rightmost city ruins following the game-ending explosion effects.
Mountain King -- There's a whole extra series of platforms to explore in this CBS game (two, in fact -- see below). Get to the very top of the highest mountain and jump to the right, once shortly, landing on the same little platform, and then once far (the latter isn't possible without the former), getting as high as possible. Some ladders and platforms will appear in the sky. Now go back to the top and repeat the jumps, but here's the trick: Coming down from the first, shorter jump, you have to land on the rightmost edge of the platform, nearly missing it, before you bound off with your longer jump. Again, stay as high as you can. Now you can catch one of the new ladders as you fall. Climb up and into a whole new game! (Granted, there isn't any scoring or quest-helping to be achieved up there, and some platforms disappear from under your feet...)
As if that weren't enough, there's another secret cluster of platforms. Go to the same highest mountain top and then drop to the platform below it, aligning yourself with the campfire above. Jump once to the left. If you were lined-up properly to begin with, you'll do an automatic long-long-jump upon landing and soar past a 4x4 group of tiny platforms hanging in midair. Hop as you hit the righthand pair; you'll jump up to a ladder. Climb up it and into the weird secret dimension.
Raiders of the Lost Ark -- Another Warshaw character is revisited here, and again, you have to look quickly. Get a parachute and the Chai (the thing in the Treasure Room that looks like a pretzel). Use the Ankh to get to the Flying Saucer Mesa (the biggest), and then drop it and put the inventory selector on the Chai. It helps to have the parachute set up as the next inventory icon to the right. Run off the mesa and drop the Chai; now immediately open the parachute so you have time to glimpse the top of the screen, where the secret character is displayed until Indy falls past the mesa-side screen.
If you go on to win the game after initiating this egg, the final screen shows the Ark rising all the way to the top, revealing the maximum possible score and thus Warshaw's initials at the bottom.
Space Invaders -- This is the second of the three "maybe bugs" I felt were worth bringing up (see Superman, below, for the third). Hold down RESET as you turn on the Atari, and you'll get two simultaneous onscreen shots instead of one.
Stampede -- Steer heads appear in place of the score if you flip it.
Superman -- Instead of starting the game by sending our hero down into the phone booth, hold down the fire button and push to the right, initiating X-Ray Vision. In early releases of the cart, once you do start the game properly after a couple seconds of this premature X-raying, Superman won't have to change into Clark Kent, the bridge will be intact, and three extra bridge pieces will be stacked over each other in the subway. You can even use them to build a new bridge over the old one if you're feeling saucy.
It's been a subject of debate: Should someone's high score (i.e. lowest time) be counted if he used this cheat? I say no.
Yars' Revenge -- Shoot a Swirl in midair, and then on the explosion screen, line your Yar up so that the little see-through square shape in the middle of his body is aligned with the line marking the point where the Swirl was hit. Usually, the game will now lock up and ol' Howard's initials will replace the score, first frontwards and then backwards.
So there you have it! Anything I forgot should definitely be sent to me. These things have always fascinated me, and I sure hope they at least interest you, or you just wasted two pages of your life. -- CF