New Super Mario Bros. Wii Cheats

Getting Stars on Your Save File

Making Mushroom Houses Appear

Save a Toad from a level where he's trapped to make a Mushroom House appear based on the last digit of the clock when you finish the level.

Unlockable levels

After you beat the game, World 9 is unlocked. Collecting all Star Coins in previous worlds unlocks the corresponding level in World 9. For instance, collect all the Star Coins in World 1 to unlock 9-1.
 

Hatless Mario

If you have 99 lives at any time, Mario will not wear his hat. Lose a life, and he'll put the hat back on.

Original End Level Fanfare

Beat the first level of the game or beat a level while rescuing a captured toadstool and the original fanfare from Super Mario Bros. 1 will play instead.