Gex: Enter the Gecko Cheats (GameBoy Color)

Enter this code at the password screen:
  Hold B then press DOWN 20 times 
  Hold B then press UP 
  Hold A then press RIGHT 
  Hold A then press LEFT twice 
  Hold B then press DOWN twice 
  Hold B then press RIGHT 
  Hold A then press RIGHT

In the first level, next to a door will be a book case. Do the tail attack on the books,
and the bookcase will retract. Flip the lever, then super-jump up to the picture of the
Mona Lisa. It will give you an option to turn it on or off.

To get full life you need to beat the game and then play the first level. Kill all the
sharks and the game will go to a blank screen. You will have maximum of everything.