New Super Mario Bros. Wii has been revealed to include an optional mode which will allow the player to let the CPU take over until the player is ready to continue..

Shigeru Miyamoto said "In New Super Mario Bros. Wii, if a player is experiencing an area of difficulty, this will allow them to clear troubled areas and take over when they’re ready. And yes, we’re looking into this for future games."

The optional mode, dubbed the "Demo Mode" is Nintendo’s way of making sure that new players don’t get stuck or find the game ’too hard’ to proceed. It is currently unknown whether this will allow the player to put the game on ’auto-pilot’ while they sit back and watch, or if it will simply show the player a way through their current dilemma.

Source: Cubed3