Fight as Mr. Karate:
Successfully complete the game without using any continues or losing any rounds.

Fight as Duck King:
Successfully complete the game as every character.

Additional options:
Unlock Duck King as a selectable character for team battle mode and data mode options.

Alternate Geese costume:
Highlight Geese at the character selection screen, then hold Start and press Circle or X for a black suit. Highlight Geese at the character selection screen, then hold Start and press Square or Triangle for a dark brown.

Alternate Geese ending:
Successfully complete the game with Geese in his alternate costume.

Alternate Billy ending:
Successfully complete the game with Billy in his alternate costume.