Might have to dust off the Wii for this one: New Super Mario Bros. Wii.
Features include four-player collaborative play (!!) and something called "demo play".
The game will also be the first game on the Wii to feature "demo play", where players will be able to pause the game, let the game complete the level for them, and resume play at any time by unpausing.
In my house, this was called the "give the controller to my 11-year-old cousin and let him show you how it's done" feature. I both hated and loved that feature. (via object of my obsession)