We all know that co-op gaming was invented in 2003 by Al Gore. The back of that placemat in IHOP told us so. It turns out, however, that some really smart computer people managed to pull off some crafty multiplayer tricks back in the 1970s, creating some of the first video games with co-op modes. And then there's us, the spoiled gamers that we are, what with our screens that display more than two colors and such. We went and had the gall to go and forget about them! Well, that ends today!
Moria
Some time around 1975, a party-based role playing game called Moria was developed for the PLATO computer system (a breeding ground for early multiplayer games). It had a text-filled interface with tons of player status information, all surrounding a stunning wire-frame first person point of view. Well, stunning for something the size of a few postage stamps, but this was 1975, remember. The story and mechanics were strikingly similar to Dungeons & Dragons and The Lord of the Rings, even though co-creator Kevet Duncombe says he hadn't heard of either until after the project started.
Here's where the fun really begins. Moria allowed parties of up to ten characters to be formed, each one controlled by a human player. One person is designated as a guide who has control over where the party goes between terrain blocks. Within those blocks are rooms that people can explore independently, killing creatures and hauling back loot at their leisure. Messages could even be exchanged via an IRC-like interface, just in case you needed to smack talk someone who wasn't being as cooperative as they should have been.
There were a few other things about Moria that set it apart from the games it was inspired by, such as Oubliette and dnd. For example, players could tie a string around an object in a room and use it to find your way back in case you got lost. Enemies in later levels can chew through the rope, however, so it's no replacement for hand-drawn maps.
Asteroids
Yep, Asteroids had a co-op mode. The tritely-classic arcade game hasn't been forgotten, but the co-op mode its console port featured doesn't get much attention. Instead of blasting 'roids all by yourself, owners of the 1979 Atari console version could plug in another paddle and shoot vector rocks as a team. Both ships were on the screen at the same time, creating a basic but effective atmosphere of cooperation. Of course, like any co-op game there were always those moments when your buddy blasted an asteroid and its shattered pieces crashed into you. That was his fault, not the game's. You should reach over and break his paddle.