Press B, Y(3), B, Y(3), Start at the options screen. Start a new game to begin at the first bonus level.
View credits and backgrounds:
Hold R + L at the options screen will appear. The credit screen will be displayed. Press Select to view different backgrounds.
Skip to level 11:
Press B(8) at the options screen. A sound will confirm correct code entry. Press Start and return to the title screen. Start a single player game to begin at level 11.
View all intermission scenes:
Press Right, Up, B, A, Down, Up, B, Down, Up, B at the title screen.
View special ending:
Hold Select and press [L + R] ten times. While continuing to hold Select, press B, A. The sound of a bomb exploding will confirm correct code entry.