Beat the 20 regular missions of Metroid Blast and 10 'Extra' Missions will become available for you.
A second player, with a wii remote, can help/distract you in most of the single player games. Octopus dance : A second player can play with the background by pointing and pressing the A button on the different objects. This will create some sound that could distract you while trying to follow the beat. Donkey Kong's crash course : A second player can point on the main player and hold the A button on your character. This will create a "slowing bubble" around your character that slows him down. Takamaru's Ninja Castle : A second player can hold the ennemies in place by aiming them and pressing the A button. It doesn't works on bosses. F-Zero Racing : A second player can destroy the many obstacles by aiming and pressing the A button. Balloon trip breeze : A second player can knock different objects out of their place by aiming them and pressing the A button.
Play 20 matches and you will unlock two more levels.
To unlock the credits you must become a star player in all 12 attractions. During the credits, you can run around and shoot stars with the L and R buttons.