All Tracks
Enter your name as CARNIVAL to unlock all tracks.

Bonus cars and tracks
Enter B, A, Z (x2), B, L, A, C-Up at the title screen. Alternately, successfully complete a circuit (in first place) to unlock additional cars and tracks. The speed of the bonus cars and difficulty of the bonus tracks will be determined by the difficulty of the race.

Bonus cars in Practice mode
Collect the stars (platinum, gold, silver and bronze) on all tracks for each difficulty to unlock the following cars.

Difficulty    Car(s)
Easy          Ghengis Kar, Pole Pos
Medium        R6 Turbo, NY 54
Hard          Bertha Ballistics, Mouse
Extreme       AMW, Toyeca

Flip in two-player or battle tag
In two player or battle mode press C-up and you'll do a flip.
Hint: it also warks to get unstuck in some levels

Mirror Tracks
To unlock mirror courses, beat Time Trial Challenge times on all reverse tracks in each circuit.

Reverse Tracks
To unlock reverse courses, beat Time Trial Challenge times on all (forward) tracks in each circuit.

Reverse-Mirror Tracks
To unlock reverse-mirror courses, beat Time Trial Challenge times on all mirror tracks in each circuit.