To play as the ganster "goofy", go to the options menu and press-up, down, left, right, and a, a.
Support Character
At the title screen, press Left, B, and Select together. The game will start with a different sound, confirming correct code entry. Now on every boss stage when you dip under 3 points of health while the boss exceeds 16, you'll receive support from a character that will fly over the screen, dropping some health. This will only trigger once per boss.