Octopounce

"The gameplay [of New Super Mario Bros. Wii] is designed to encourage a fluid combination of cooperation and competition. The one game we had a chance to try at the IndieCade booth, Octopounce, features almost the exact same friendly-competition between jumping characters -- and it was released two months before anyone knew about Miyamoto's latest." -Engadget

Octopounce is an ultracasual four-player platform game for big events. It was first created for Giant Robot San Francisco's Game Over / Continue? show (in 2009) as a collaboration between anna anthropy and Saelee Oh.  It accommodates up to four players at once, but players are free to drift in and out of the game at any time.

You are an octopus. Catch fish. Catch birds. Work together, or compete, or both.