Big Head Mode - After getting the four hidden characters and the last
boss, use these characters to finish the game once each, then a new option
will show up to allow you to play the Big Head Mode.
Hidden Characters - To play as Jacky, Sara, Bun Bun and Jeffry, set the
Game Level to Normal or higher, then use each character to beat the game.
Play as the Boss - To play as the final boss, set the Game Level to
Difficult, Number of Rounds to 2 or higher, then finish the 1P game.