WarioWare Inc.: Mega Party Game$ Cheat Codes for Gamecube

Easier Time in the Basketball Microgame
To successfully beat the basketball game, press A when you hear a noise on your first or second jump.
submitted by: Brian

Sound test:
Go through every multi-player mode to unlock the "Sound Test" selection at the options menu.

Play any mini-game:
Get a rose from all the mini-games in practice mode to unlock the final single player mode door. Use the final door to play any mini-game again.

Nintendo game tester high scores

Game Modes:
All Mixed Up: 63
Hard: 34
Thrilling: 40
Time Attack 20 games: 1'23''83
Time Attack 40 games: 2'35''29
Time Attack 60 games: 4'08''38
Master Mode: n/a

Individual Games:
(Intro/Wario) Wario Wear: 53
(Sports/Jimmy) Fruit Shoot: 55
(Sci-Fi/Dribble & Spitz) Classic Clash III: 501
(Strange/Mona) Boom Box: 34
(Nintendo/9-Volt) Mario Paint: Fly Swatter: 44
(I.Q./Orbulon) Gear Head Fred: 71
(Reality/Dr. Crygor) Hard Core: 250
(Nature/Kat & Ana) Spunky Monkey: 249
(Anything Goes/Wario): n/a