Play as Dr. Doom
Beat and save the game under the default settings. Then, turn off the "Shortcuts" option. Now go to the character selection screen and press Down, then press Down again and hold the button. While holding that button, quickly press X, Circle, R1 in that order, holding each button down as the next button is pressed. At this point, Down + X + Circle + R1 should be held on the controller. If you entered the code correctly, the words "Captain America" will be spoken, but Dr. Doom's face and name will appear.

Play as Thanos
Beat and save the game under the default settings. Then, turn off the "Shortcuts" option. Now go to the character selection screen and press Up, then press Up again and hold the button. While holding that button, quickly press L1, Triangle, Square in that order, holding each button down as the next button is pressed. At this point, Up + L1 + Triangle + Square should be held on the controller. If you entered the code correctly, the words "Spider Man" will be spoken, but Thanos' face and name will appear.

Play as Anita (Japanese version)
Enable the "Fight as Dr. Doom" and "Fight as Thanos" codes. Then, turn off the "Shortcuts" option. Now go to the character selection screen and press Up, Right, Down, Left, Up, Right, Down, Left, then hold Up. While holding that button, quickly press Square, Triangle, L1 in that order, holding each button down as the next button is pressed. At this point, Up + Square + Triangle + L1 should be held on the controller.

Disable vs. mode power gems
Before the match begins, press Select on controllers one and two. If you entered the code correctly, the phrase "No Gems" will appear.

Continue fighting
After the last round of the match ends, hold Select to continue hitting your opponent.

Alternate costumes
Turn off the "Shortcuts" option. Then at the character selection screen, hold Up (if your character is in the upper row) or Down (if your character is in the lower row) for three seconds and press any button.

Throw pumpkins
Use a reality gem, then press Select.