Go to the options menu, either in game, or on the main menu. Hold L1+R1 (camera up + zoom in) and press the following:
Invincibility: Triangle, X, Triangle, X
Blow up cars on impact: Triangle, Triangle, Square, Square
Unlock the red brick car: Circle, circle, triangle and square
Alternate Audio during Credits: X, Square, Square, Triangle
Alternate Views: 0, O, O, X
Drunk Driving: triangle, 0, triangle, 0
Grid Mode: O,X,O,Triangle
High acceleration: Triangle, Triangle, Triangle, Triangle
No top speed: Square, Square, Square, Square
Press L3 (horn) to make car jump: Square, Square, Square, Triangle
Speedometer: Triangle, Triangle, 0, Square
Cheats for the PC
Enter the Options screen and hold F1, then enter the following with the arrow keys. Note: This may crash the game. To avoid this, start a new game and enter the codes at the in-game options screen.
Up - Up - Up - Up: All cards (after beating the game)
Left - Right - Left - Right: All character costumes (after beating the game)
Up - Down - Up - Down: All vehicles (after getting 100%)
Down - Down - Down - Up: Different camera angles
Down - Down - Right - Left: Drive a toy car
Right - Right - Right - Right: Higher acceleration
Right - Up - Right - Up: Invulnerability
Left - Left - Left - Left: No top speed
Right - Right - Left - Left: One hit destruction
Down - Down - Down - Left: Play As Any Character
Left - Left - Left - Right: Press horn to jump
Right - Right - Down - Left: Speedometer
