The Death And Return Of Superman

Cheat mode:
Play the "0B", "29", "2C", and "05" selections in order on the sound test screen.

Full energy, life, and special powers:
Enable cheat mode and press A + B + X + Y during game play. You will also be invincible during the missions when you fly in the sky, shooting the robots.
Information in this section was contributed by Huntr631.

Level skip:
Enable cheat mode, then hold A + B + X + Y and press Select during game play.

Hint: Defeating the Bosses:
Use the following technique to defeat Doomsday and the other Bosses quickly. Use Superman's eye beams, hand blasts, or other special attacks. Time them to connect when the Boss is almost on Superman. If done correctly, Superman will be able to hit him until he falls. Then, repeat this process until the Boss has been defeated.
Information in this section was contributed by Jesse Smith.