Most aspects of Missile Command and Centipede were wildly dissimilar. The themes couldn't be more different: the fears of Cold War reality versus a fantastic, magical mushroom forest populated by neon bugs. Missile Command allowed player movement over the whole screen, while Centipede restricted it. Counting up bonus points gave players a brief respite in Missile Command, while in Centipede, the action was continuous. However, the two did have a few things in common. In both games, the object was to eliminate threats from the top of the screen before they fell too far and the situation became unmanageable. The biggest similarity was the trackball control scheme, though Missile Command did have two more fire buttons than Centipede did.
It was this shared control scheme that would bring the two game concepts together over a decade after their original release. In 1992, Atari developed a game to celebrate its 20th anniversary, and rather unimaginatively titled it Arcade Classics. Two games were included: Super Centipede and Missile Command II. Neither of these had been released before; Millipede was the only Centipede sequel, and Missile Command had no direct follow-up. For the most part, these sequels offered the standard graphical update, with an improved background here and there, and that was pretty much it. (After all, if it ain't broke, etc. etc.) But there was one major improvement to each game: co-op gameplay!
As you can see from the screenshots, both Super Centipede and Missile Command II allowed a second player to join in. For the first time, you and a friend could team up to take down incoming missiles or runaway arthropods. This would have made a huge difference in the difficulty of both games, adding to the playtime per quarter, I would imagine, unless the speed of the game were increased and more frequent enemy appearances were tweaked to accommodate the extra player. Unfortunately, most people never had the chance to try either of the two new games included in Arcade Classics, either with a friend, or alone. According to the data at the Killer List of Video Games, Atari made only a handful of cabinets, and the game never made it to mass production. I've been unable to find too much information about Arcade Classics, but as a fan of co-op coin-op, I certainly wish this game was more widely available. A two trackball cabinet based on fondly remembered classic games like Centipede and Missile Command would have been quite unique compared to the sea of Street Fighter clones so widespread in arcades in 1992.
All was not lost, however. The fusion of co-op gameplay with these classic single player games from the Golden Age would turn up in due time. Centipede itself was remade and significantly overhauled in the late 90s. This new version of Centipede was a major overhaul, but critically panned, though it did include split-screen co-op. More recently, for Missile Command's 30th anniversary, a free online version of the game was developed, and this more faithful remake allows for extremely frantic seven player co-op action! Still, it's shame that Arcade Classics was never widely released. The ROMs for the prototype are probably available somewhere, but a two-trackball arrangement in a MAME cabinet would be difficult to find in order to have the complete, authentic arcade experience. Perhaps someday we'll be able to experience Super Centipede and Missile Command II as they were originally intended, but for now, the two remain but a footnote in the history of Co-Op Classics.