MDK cheats and cheat codes for Playstation

Select any level
Hold L1 + L2 + R1 + R2 at the main menu, then press Triangle, Up,
Triangle, Circle, Right, now immediately release L1, L2, R1, and R2
when the level select text appears.

Invincibility
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Circle, Triangle, 
Triangle, Circle, Right, Up, Left, L1, Square.

Bonus air strike
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Down, Up, Circle, 
Down, Up, Down, L1. 

Bonus air strike
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Triangle, Right,
Circle, Left, Left, Circle, Triangle, Triangle, L1, Right. This cheat 
may only be enabled during the last stage of the game.

Seal
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Circle, Triangle, 
Triangle, L1, Right. This cheat may only be enabled during the stage 
of the game. 

Bones seal
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Triangle, Right,
Circle, Left, Left. 

Earthworm Jim cow power-up
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Up, Down, Down, L1, 
Right.

Dummy decoy
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press X, L1, Right, Circle,
X, Up, Square. 

Super chain gun
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Left, L1, Down, 
Square, Triangle, Up, Down. 

Grenade
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Triangle, Circle,
Square, L1, Right. 

Sniper grenade
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Up, Square, L1, Left,
Circle, Triangle. 

Homing sniper grenade
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Left, Up, X, Square,
L1, R1, Right. 

Thumper weapon
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Down, Up, Left, Left,
Triangle, Up, Right, Down. 

Twister weapon
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Down, L1, Square,
Triangle, Right, Up, X. 

Super gun
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Right, Up, Down, L1,
Down, Circle, Left, Left. 

Homing bullets
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Square, L1, L1, Right.

Nodie
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Circle, Triangle, 
Triangle, Circle, Right, Up, Left, L1, Square.

150 hit points and extras
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Square, Triangle,
L1, L1, Left, Square, Triangle, Circle, Right, L1.

Show coordinates
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Down, Down, Triangle, 
Triangle, L1, X, Triangle. 

Disable opponents
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Up, Square, L1, Left,
L1, Square, Square. 

Strange mode
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Left, Circle, X.

Maximum hit points
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Right, L1, Square,
Triangle, L1, Down. 

Faster speed
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Right, Circle,
Triangle, Circle, X. Press R2 during game play to activate faster
speed. 

Mortar
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Left, L1, Triangle,
Square, Right, Circle, Left, Left.

World's smallest nuke
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Down, Up, Square,
Triangle, Down, Circle, Circle, Right.

World's most interesting bomb
Pause the game play, then press L1, Up, Square. Resume the game and
immediately pause the game play again. Then, press Down, Right, Circle, 
Circle, Left, Left, Up, Square, Triangle.

Invincible mode
Pause the game play, then press Down, L1, Up, Square. Resume the game
and immediately pause the game play again and press Circle, Triangle, 
Triangle, Circle, Right, Up, Left, L1, Square.