Reach the water stage on level two. Fly across the water until reaching a yellow square marked with the letter 'E'. Steer your ship behind the square and press Up. If your ship was positioned correctly, it will warp to a bonus level.
Press Start at the title screen. Highlight the 'System Configuration' option, then hold R and press Start. Press L + R on controller two at the system configuration screen. The current stock, credits, and stage will appear. Hold A + B + X + Y (in that order) on controller two. The number of ships may now be increased to thirty and credits may be increased to ninety-nine. Any of the eight missions may also be selected for game play.