When you see, in second level of Diamondas, three blue trampolines jump on the first one. While our hero floats in the air, head to the left wall, jump in and shoot the sign '?'.
This cheat only works on 1 player.
Type "JJ" before the description...
JJFLY -Enables you to fly using your ears(on the first time you time JJFLY and on the second time you type it, you will be floating with a anti-gravity skateboard)
JJCOINS-gives you an amount of coins
JJGEMS-gives you some colored gems
JJMORPH-enables you to switch from Jazz into Spaz and to Lori (another version) and to a frog (if I am right)
JJAMMO-gives you tons of ammo for a basic weapon.
I hope I helped a lot!