Cheats are unlocked by completing all mission objectives (not just the primary objectives) within a certain time. To activate the cheats, go to "System Options" > "Extras" > "Cheat Grid". To play the FMV sequences unlocked in the cheat menu, choose the "Movie Player" option that is above "Cheat Grid".

CHEAT FUNCTION - HOW TO UNLOCK
Saliva Spy Hunter Video - Complete level 1 in 3:40.
Green HUD (Heads Up Display) - Complete level 2 in 3:35.
Saliva Your Disease Video - Complete level 3 in 2:40.
Night Vision - Complete level 4 in 3:15.
Early Test Animatic Video - Complete level 5 in 3:25.
Extra Cameras - Complete level 6 in 3:45.
Rainbow HUD (Heads Up Display) - Complete level 7 in 3:10.
Inversion Camera - Complete level 8 in 3:05.
Concept Art Video - Complete level 9 in 3:45.
Fisheye View - Complete level 10 in 3:15.
Camera Flip - Complete level 11 in 3:10.
Puke Camera - Complete level 12 in 3:30.
Making Of Video - Complete level 13 in 2:15.
Tiny Spy - Complete level 14 in 5:10.
Hover Spy - Complete the entire game.
Super Spy - Complete all 65 objectives in the game for unlimited ammunition and invincibility for your car.