Yesterday, I saw nine people play a single Wii U game. How'd they do that? One person (in this case Game Trailer's Andrea Rene) on the Wii U GamePad, and then four pairs of people sharing Wii Remotes and Classic Controllers.
I should have shot this in panorama so that you could see all nine people. Sorry!
The game is called Runbow; the development studio is 13AM games. What they've done here is clever, since the Wii U itself thinks that it's attached to a GamePad and four controllers. But since each Classic Controller has to be tethered to a Wii Remote—and since there are buttons on both—the developers are able to let a pair of people wield each controller-Remote combo. The devs also say you could use a Nunchuk instead of a Classic Controller.
What's the game? Here's some gameplay:
Runbow can be played solo, but the mode here is a competitive race, with each player trying to get far enough ahead to clip the trailing players out of action. The optional GamePad player can then drop bombs and otherwise try to stop the eight runners from reaching the end of the level. Oh, and when the scenery's color filter changes, platforms of that color disappear.
There you go. A nine-player local co-op game. What more do you need?
Runbow is slated for release in the third quarter of this year.