All codes below are done when game is paused, unless otherwise noted:
During gameplay, pause the game and press X + Y at the same time. This works in all modes. In four-player mode, the person who paused must enter the code.
If you complete all the missions, a secret extra mission will be unlocked, where you get to race around a garden as a snail.
Insert the CD into your CD Rom Drive and open it up to see icons, screenshots, logos and artwork.