Finish a fight and at the Continue screen hold R X A until the next match starts.
Hidden Options Mode
When the fighter's h3s appear in OnePlayer Mode press X A L.
Fight Against the CPU in Duel and Team Modes
At the Character Selection screen hold L R to control the other player's selection then press Y to select your opponent's character. Now that character will be controlled by the CPU.
Highlight Story Mode hold L R and press Start.
At the Title screen hold L R and press Start. Keep holding L R until the Debug Menu appears.
At the Character Selection screen hold L R and press Left or Right.
Fight as Same Character
Select the same character then hold L R on Controller One and press any button to start the match.
Extra Difficulty Levels
At the Options screen press L R Select.