The following are known Game Genie Codes for Mario is Missing! on Super Nintendo (SNES).

• Talk To Someone Once To Learn All They Know (All 4 Checks Appear On Computer For That Person)
  CB8D-17DF
  EE8D-170F
  3C8D-176F
• Use Computer To Access Any Facts Except Pamphlets (No Checks Appear On Computer)
  6D8D-C4AF
  DD80-C70F
  DD85-C4DF
• Use Computer To View Pamphlets On Any Artifact (No Checks Appear On Computer)
  6D82-17AF
• Always Get Yoshi After Using Globulator
  DFED-4D04
• Pick Up One Artifact And Get All Three
  CB8E-47AF
  EE8D-1DDF
  3C8D-1D0F
• Leave Level As Soon As You Enter To Complete Level
  DDB8-3705
  6DAA-C707
  Note: You do not need Yoshi if you enter the pipe as soon as you come out of it.