View all intermission scenes
Press Right, Up, B, A, Down, Up, B, Down, Up, B at the title screen.
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.
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.
X*Bert mode
Press B, Y(3), B, Y(3), Start at the options screen. Start a new game to begin at the first bonus level.