When you open the Game, go to options and then go to Passwords. Change the letters in the boxes to enter the cheat. Enter the cheats below:
Code - Effect
SLSDRDL - The game gets really hard
DSRDMRM - Turtles don't suffer any damage from things
MRLMRMR - Everything that increases your health Turns into pizzas
DRMSRLR - Your health recovers gradually
Play as Casey Jones
Win the Open Brawl Tournament. Alternately, Casey Jones is unlocked five days after a saved game file is created; you can change the system date to do this. Casey Jones replaces Raphael.
Play as Karai
Defeat Karai in the Foot Fight Tournament in less than 150 seconds. Alternately, Karai is unlocked thirty five days after a saved game file is created; you can change the system date to do this. Karai replaces Michaelangelo.
Play as Slashuur
Win the Battle Nexus Tournament. Alternately, Slashuur is unlocked forty five days after a saved game file is created; you can change the system date to do this. Slashuur replaces Leonardo.
Play as Splinter
Successfully complete level 11-7. Alternately, Splinter is unlocked ten days after a saved game file is created; you can change the system date to do this. Splinter replaces Donatello.
Unlock original TMNT arcade game
When on the rooftops in stage 9-1, start smashing the many crates to find an artifact. Take that artifact back home, and give it to April. Once she appraises it, she'll tell you that it is the original TMNT aracde game. Now go to the title screen, and go under options. The original TMNT arcade game will be there.