Successfully complete story mode to unlock that wrestler's alter ego.

Becky: Candy Cane
Dr. Cutter: Anesthesia
Judgment: Bloody Shadow
Killer Khan: Aigle
Mistress Spencer: Miss Spencer
Noble Rose: Evil Rose
Rowdy Reiko: Reiko Hinomoto
Sgt. Clemets: Dixie Clemets
Showbiz: Aisha
The BBD: Makoto Aihara
Lady X: Lady X 2

Successfully complete story mode to unlock that wrestler's alternate costume, bikini, and alternate bikini in any stage.

Press Left + Triangle or Left + Triangle.
Press Circle while running.

During any match, leave the ring and get any weapon out of the corners. When your opponent comes to you, press Up or Down + Square to attack. Three successful hits will fill your Lethal Move indicator one level. The maximum amount is five.

Successfully defend a title.

Enter the gallery with any character and allow the game to idle. The screen will eventually get a fuzzy white border the girl will tell you various things about herself.

Win the title in exhibition mode.

Press Circle when in a corner outside of the ring, or near a weapon that has been dropped.

During bouts that take place in a ring (not the mud pit), leave the ring and run to either the top corner (to get the tickle stick) and wait for your opponent to come out to get you. Press Up or Down when you attack (otherwise you will just bludgeon your opponent and will not humiliate them). Two successful uses will fill the opponent's humiliation gauge and have your Lethal Move indicator almost full. The tickle stick is least likely to be blocked.

Successfully complete story mode with all the default characters.

Press Circle after getting knocked down near the ropes.

Select exhibition mode. Choose "Normal Match" or "Title Match", then "1 player", "2 player", or "Computer". Next, choose the characters to have their entrances switched. Choose a ring, then hold L1 + L2 +R1 + R2 while selecting the "Play" option.

Press Up + Square or Down + Square with a weapon.