Genesis,
To access the debug menu, go to the START/OPTIONS screen and select the option menu. Put the cursor on "Done!!" and press code Left, Down, Left, Right, Down, Right, Left, Left, Right, Right.
Fergality
To do a fergality, enter Test Mode, then change the background to 6 and enable the "Ooh Nasty" option. Next choose Rayden as your character and finish your opponent with Away, Away, Away, Block.
Test Mode
Go to the options menu and move down to done. Press Left, Down, Left, Right, Down, Right, Left, Left, Right, Right. If done correctly, the words "TEST MODE" will appear.
Warp to Shao Kahn
At the Options menu, press A, B, C, C, C, B, B, A, A, A, A. When Shao Kahn appears, quickly press B to go to the final stage.
Snes
30 Credits
At the character select screen, quickly press Left, Up, Right, Down, Left, Select. If you did it right you'll hear a gong sound.
4X4 Match
At the Game Start screen, hold L + R and press Start. A 4X4 match should begin. Note that this is for two players only, and the computer will not participate.
Choose Your Fights
To fight any of the characters below, enter the indicated code on the Character Select screen.
Opponent Code
To fight any of the characters below, enter the indicated code on the Character Select screen.
Jade Up, Down, Down, Left, Right
Noob Saibot Left, Up, Down, Down, Right
Kintaro Up, Down, Down, Right, Right
Shao Kahn Right, Up, Up, Right, Left
Double Fatality Time
Need more time to enter the Fatality codes? At the Character Select screen, press Up, Up, Left, Up, Down + Select.
Play as Shoa Khan
To play as Shoa Khan go to the Options menu and put the Handicap at max the at the player select choose Sub-Zero but press the B-button twice.
Super Damage and Defense
Sticks and stones may break your bones, but a tactical nuke is much better.
To defeat any opponent in two hits, press Down, Up, Right, Up, Left + Select at the Character Select screen. This code will also halve any damage you receive.
Warp to Jade
At the character select screen, press Up, Down, Down, Left, Right + Select.
Warp to Smoke
Press Up, Left, Up, Up, Right + Select on the Character Select screen.
Credit to
IGN.com