Wii Party Cheats - Wii

Unlock Difficulty Levels
Expert Difficulty - Beat CPU players set to Advanced in a Party Mode.
Master Difficulty - Beat CPU players set to Expert in a Party Mode.

Unlock Minigames
To unlock additional minigames for Challenge Mode, you simply have to play their normal version in any mode:

Banana Blockade (2-players) - Play its normal version in any mode.
Clover Hunt (1-player) - Play its normal version in any mode.
Shifty Gifts (1-player) - Play its normal version in any mode.
Tippy Traverse (2-players) - Play its normal version in any mode.

Spot the Sneak in Minigames Mode
Play every 4-Player game.

Unlock Balance Boat: Time Attack Mode
Balance Boat (Time Attack: Expert) - Beat Balance Boat (Time Attack: Intermediate).
Balance Boat (Time Attack: Intermediate) - Beat Balance Boat (Time Attack: Beginner).
Balance Boat (Time Attack) - Beat Balance Boat on Expert.