Octopounce, by game designer Anna Anthropy and artist Saelee Oh, allows up to four players to control a little pixel octopus in a hand-painted underwater backdrop. The goal is to jump up and catch as many fish as possible, and each player can bounce on the other characters to reach the fish. Inactive player avatars remain on the screen, sleeping, so they can be used as convenient platforms. There's no real score -- an octopus becomes more opaque as it eats fish, and commentary about the game's progress appears in a text crawl at the bottom of the screen.
Of course, NSMB Wii features divergent gameplay elements, like precision platforming and enemies, but in terms of the newest mechanic -- the multiplayer bouncing -- this game, designed for the Game Over/Continue? exhibit during GDC, anticipated that element before Nintendo revealed it. It sort of makes sense, then, that Octopounce is inspired by Super Mario War, a homebrew effort to make a multiplayer Mario experience -- but NSMB Wii resembles Octopounce more closely than it does Super Mario War.