All Cars, Tracks and Difficulties
At the Mode Select screen, press L, Z, R,C-UP, C-DOWN, C-LEFT, C-RIGHT, START. You should hear a chime if you did it correcly.

Change Car Colors
To change your car's colors, simply press the R-Button during the car customization screen. Note that there are only a few select colors for each vehicle.

Joker Cup
To get the Joker Cup and six additional tracks beat the Jack, Queen, and King Cup on Standard difficulty.

Mute City II Shortcut
Right after you make the third hard turn, you will see a ramp to the left that looks like it will lead you off track. If you hit it with a booster, you will fly over the gap and onto the next strip of tracks.

Rotate Cars on Customization Screen
Want to see your car from different angles? At the customization screen press the C-Buttons to rotate the car in all directions.

Smaller Cars
At the car select screen press and hold the (L) and (R) buttons. While holding those buttons press C-LEFT and C-DOWN to shrink the cars.