Play as the old character:
Highlight Rayden, Jax, Kung Lao or Kano. While highlighted, press select. You can now play as the old characters.

Level Select:
To select your starting level in 1-player or Vs mode, highlight Sonya and pressing Up + Start.

Unlimited Credits:
(submitted by: _IMP_[TML])
Press Down, Down, Up, Up, Right, Right, Left, Left at the Story screen.

Chameleon Kode:
Choose any male ninja. Hold back (on D-pad) R1, R2, triangle, and square until character changes color.

Blue Question Mark Screen:
Hold down L1, L2, R1, R2, and up on the D-pad until the screen shakes.

Select Battle Arena:
At the character select screen, choose Sonya. Press up on the D pad and push the start button. The screen will shake and make a noise. After you select your fighter, you can choose your battle arena.

Fatalitie:
(submitted by: _IMP_[TML])
Enable One button fatalities from "?" menu. Animality - Run
Babality - LP
Brutality - HP
Fatality 1 - HK
Fatality 2 - LK
Friendship - BL

? Kube:
(submitted by: Thomas OCampo)
Hold Up + R1 + R2 + L1 + L2 on the square labeled “Konfigure Kombat” in the Options menu. (A shaking screen confirms correct entry.) The “?” menu will open, allowing the following options to be set. One button fatalities – finish your opponent with one hit.
Instant aggressor – Aggressor meter will flash after one hit.
Normal boss damage – Bosses inflict the same amount of damage a normal fighter would inflict.
Low damage – Character sustains minimal damage from opponent’s attacks.
Health recovery – The health meter is gradually replenished with each hit.