Classic NES Series: Metroid Cheats

Unlock Samus with bonus weapons:
Submit the password JUSTIN BAILEY ------ ------ to unlock Samus at Ridley's Lair.

Super password:
Enter NARPAS SWORD0 0000_ _ _ _ _ _ _ _ as a password. REMEMBER: "_" indicates a space, and except for the letter "O" in "SWORD", the remaining characters are the number zero. You will start at the beginning of the game with unlimited life, unlimited missiles, and all upgrades. The word in this is "NAR PASSWORD". "NAR" is an abbreviation for the name of the person who designed the password system, Tohru Narihiro.
User Cheat by PhillyBoy

Alternate game:
Submit the password 999999 999999 KKKKKK KKKKKK with no Varia suit and a different ending.

Quick save:
Press Start to pause your game, then press Select + Up to display your current password.