Here are some cheats and tips for the game Classic NES Series: Metroid.
Play as Samus with bonus weapons:
Enter “JUSTIN BAILEY —— ——” as a password to play as Samus at
Ridley’s Lair.
Super password:
Enter “NARPAS SWORD0 0000_ _ _ _ _ _ _ _” as a password.
Alternate game:
Enter “999999 999999 KKKKKK KKKKKK” as a password with no Varia suit
and a different ending.