All Working Mario Party 8 Cheats - Wii

Unlock Characters and Maps
Bowser's Warp Orbit - Beat the Star Battle with any character
Blooper/Hammer Bro - Beat Star Battle with any character. For the second character, beat Star Battle again with the first one you unlock.

Unlock Minigames
The following are minigames that can be unlocked in the Minigame tent:

Crown Showdown - Unlock at last one minigame in the 4 player, 1 vs. 3 player, 2 vs. 2 minigame and Duel minigame categories.
Flip Out Frenzy - Unlock at least one 4 player minigame.
Test For The Best - Unlock this mode in the Fun Bazaar.
Tic Tac Drop - Unlock at least one Duel minigame.

Minigame Wagon
When you beat Star Battle mode, you can buy minigames in the Minigame Wagon. This is helpful if you feel impatient to or if you do not want luck to try and and get a certain minigame for you on a game board.