Pokemon Blue Version Cheat Codes & Secrets

Beneficial Glitches and Exploits

Pokemon Blue has no button-code cheat system — its legendary “cheats” are all discovered glitches that Gamefreak never patched. These work on original cartridges and all major emulators.

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Item Duplication (MissingNo. / Old Man Glitch)

The most famous glitch in Game Boy history. Duplicates the item in your 6th bag slot, setting its quantity to 128 (the byte overflows, but items like Master Balls cap safely).

Setup:

1. Place the item you want to duplicate in bag slot 6 (Rare Candy or Master Ball recommended)
2. In Viridian City, speak to the old man blocking the road — tell him you are not in a hurry
3. Watch his Weedle-catching tutorial to completion
4. Immediately open the menu and Fly to Cinnabar Island — do not enter any building or battle first
5. Surf along the eastern coastline of Cinnabar Island (the border between land and sea on the right edge)
6. Wild encounters will trigger — these are glitch Pokemon including MissingNo. and various high-level monsters
7. After any encounter on those tiles (flee, catch, or faint it), your 6th bag slot item quantity becomes 128

Why it works: The old man tutorial temporarily replaces your trainer name bytes in RAM with “OLD MAN.” Your actual name characters are shuffled to a VRAM location. The glitch coastline tiles read those VRAM name bytes as Pokemon encounter data, so your name literally determines which glitched Pokemon appear.

Name-to-Pokemon mappings (Cinnabar coast encounters):

Name Character	Pokemon Encountered
A	Slowbro (L. 26) or MissingNo.
B	MissingNo.
C	Rhyhorn (L. 3 or L. 28)
G	MissingNo.
W	MissingNo. (L. 152 and L. 153 variants)
h	Jynx (L. 14 and L. 13)
p	Tentacool (L. 18)

Warning: Catching MissingNo. can corrupt your Hall of Fame data. Viewing its Pokedex entry can freeze the game. Simply fleeing every encounter is the safest way to get the item duplication without save corruption risk.

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Mew Glitch (Get Mew Without a Nintendo Event)

Mew has internal index number 21 and a Special stat of 21. The Trainer-Fly exploit exploits how the game tracks Special stats to force a Mew encounter.

Steps (Route 8 Method):

1. Have a Pokemon that knows Fly in your party
2. Have not yet defeated the Youngster west of Nugget Bridge in Cerulean City (the one with a level 17 Slowpoke)
3. Travel to Route 8 (the road between Lavender Town and the Underground Path entrance near Celadon)
4. Stand directly in front of the Underground Path door on Route 8
5. Take one step toward the Gambler trainer (the one near the door) — he will turn and begin walking toward you, triggering the ”!” exclamation
6. Immediately press Start before the battle begins (timing is tight — save right before if needed)
7. Use Fly to escape to Cerulean City while the Start menu is open
8. Go fight the Youngster with the Slowpoke near Nugget Bridge and defeat him
9. The game will now lock the Start menu — this is normal
10. Fly or walk to Lavender Town, then walk west onto Route 8
11. The moment you step onto Route 8, a wild battle triggers automatically — it is Mew at Level 7

How it works: Escaping a trainer’s sight line mid-trigger corrupts the Special stat tracking variable. The Youngster’s Slowpoke has a Special stat that sets this variable to 21, which maps exactly to Mew’s internal species index.

Mew’s Moveset when caught this way:

Move	PP
Pound	35
Transform	10

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Safari Zone Exit Glitch

Running out of Safari Zone steps normally ejects you and forfeits all caught Pokemon. Use this to avoid the timeout.

1. When your step count is running low, use Dig or Teleport to exit the Safari Zone before the warden’s message appears
2. All Pokemon caught during that session are kept in your PC boxes
3. Re-enter and repeat as needed

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Trainer-Fly Variants (Other Pokemon)

The same glitch used for Mew can obtain other Pokemon by manipulating which trainer you defeat after the escape. The Pokemon you encounter is determined by the Special stat of the last Pokemon you battled before returning to the trigger area.

Target Pokemon	Special Stat Needed	Easy Source Trainer
Mew	21	Youngster’s Slowpoke (Special 21)
Nidoran♀	16	Route trainer Ekans
Cubone	40	Route trainer
Koffing	40	Rival’s Koffing (Pallet Town)
Gengar	95	Ghost tower encounters

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GameShark Codes

These codes require a GameShark v3.0 or compatible device for original Game Boy hardware. For emulators, enter them as Game Genie or GameShark cheats in the cheat menu.

Code	Effect
0115D7CF	Wild Pokemon is always Bulbasaur
01997CD8	Wild Pokemon always at level 153 (forces overflow to level 1 effective)
0101D8CF	Wild encounters replaced with Bulbasaur (index 01 in hex = Rhydon internally — swap hex value for target)
01287ED3	Walk through walls
01FF16D0	Infinite money
010FF3CF	Item slot 1 quantity set to 255

Wild Pokemon modifier: Replace the first two digits (after 01) with the internal hex index of the Pokemon you want:

Internal Hex	Pokemon
99	Bulbasaur
09	Blastoise
B0	Mewtwo
15	Mew
54	Pikachu

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Developer Easter Eggs and Hidden Content

Jack Frost and the Slot Machine RNG: The slot machines in Celadon Game Corner are not truly random — the game cycles through a fixed RNG sequence. Pressing A at specific moments (tied to the frame counter) dramatically increases jackpot rates. Long-press A during the reel spin to attempt to stop reels on 7s at the optimal internal frame.

Unused Pokemon Cries: Several internal sound entries exist for Pokemon that were cut before release. These are accessible only through memory editors but are present in the Blue ROM.

S.S. Anne Truck: A truck sits inaccessible near the S.S. Anne dock. Rumors of a hidden item or Mew under it are false — the truck has no interactive data and exists only as background scenery, likely a placeholder that was never removed.

Pallet Town Surfing Easter Egg: Surfing south of Pallet Town leads to an otherwise unreachable water route. No game content exists there; the area was intended for a cut feature. You can reach Cinnabar Island from here without using Fly.

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Password System

Pokemon Blue uses a save file system, not passwords. Progress is written to battery-backed SRAM on the cartridge. There is no level select or password entry screen. The closest equivalent to “codes” is the Game Link Cable Mystery Gift (Japan-only feature) and the Nintendo event distribution for Mew and Surf Pikachu, which required physical attendance at sponsored events in 1996–1998.