Enter the following at the password screen:

LDMSLRDD --> A single hit from enemy attack means death.
SLLMRSLD --> All healing items turn into temaki sushi.
MSRLSMML --> Enemies' attack power doubled.
SLRMLSSM --> Enemies' defense power doubled.
DMLDMRLD --> Healing items are no longer available.
RRDMLSDL --> Ougi gauge is always full.
LLMSRDMS --> Shuriken no longer available.
LMDRRMSR --> Turtles can carry unlimited number of shuriken.
MDLDSSLR --> Turtles no longer take damages.