MissingNo.
Surf up and down the east coast of Cinnabar Island, right after you let an old man in Viridian City demonstrate how to catch a Weedle, and the water coughs up something that should not exist. The game went looking for a Pokemon in a place where none was ever written, and it found the empty space between the code. This is a full teardown of that empty space, pulled straight from the cartridge.
Everything on this page was read out of a real Pokemon Red ROM by reproducing the game's own broken logic, the same out-of-bounds reads the Game Boy performs when it meets MissingNo. Nothing here is folklore or guesswork. Where five different cartridges disagree, I decoded all five and show you the differences.
Watch the game build a Mon
Before we can explain what breaks, you have to see what normally works. Every Pokemon sprite in Red and Blue is stored compressed, as two black-and-white layers stacked into one grayscale picture. The Game Boy rebuilds it live, in a few thousandths of a second, with a little decompression engine. Scroll, and watch a real one come together tile by tile.
Now feed it garbage
Here is the whole secret of MissingNo. in one sentence: the machine you just watched does not check whether its input is a sprite. When you meet MissingNo., the game reads a size and a location for its picture out of the empty slot in the species table, and those numbers point at data that was never a sprite. The decompression engine runs anyway. It unpacks, it delta-decodes, it stacks the layers, exactly as before, on bytes that mean nothing.
Watch the whole machine run on nonsense. It fills the first one-bit buffer, then the second, decodes the deltas, and stacks the two layers into the final two-bit sprite, the exact pipeline you watched build Gengar. What comes out is this: MissingNo.'s actual sprite, decoded honestly from the ROM. There is no creature waiting inside, just structured static, because even garbage run through a real algorithm comes out with a strange, banded texture rather than pure noise. The most famous glitch in gaming is not a special effect. It is an honest machine doing its job on dishonest data.
This is the deterministic version, decoded from fixed ROM data. What most players actually saw on screen looked different again, because the game then squeezes this oversized image into a smaller display window and, for some encounters, reads from video memory instead of the cartridge. The shape it shows you is this same data, wrapped and sheared by that final step, which is why it never resembles a clean piece of what you see above.
The three faces it can wear
MissingNo. is not a single creature but an empty slot, and thirty six different empty slots all lead to it. Most produce the static above. But three of those slots hit a special case the developers wrote for entirely different reasons, and those three give MissingNo. a real, finished sprite: the two dinosaur skeletons from the Pewter City museum, and the ghost that haunts Lavender Tower before you have the Silph Scope. Each of these has its own full page in the Glitchhouse.
The anatomy of an accident
When you meet MissingNo., the game reads twenty eight bytes of stats from a table, at a slot that holds no real Pokemon. Because the empty slot is numbered zero, and the game does its arithmetic in single unsigned bytes, zero minus one wraps around to two hundred fifty five, so it reads entry two hundred fifty five, far off the end of the intended table. Here is what it finds.
| What the game reads | Where | Value it gets |
|---|---|---|
| Its type | stats byte 7 | BIRD a type cut from the finished game |
| Attack | stats byte 2 | 136, higher than Mewtwo |
| Defense | stats byte 3 | 0, none at all |
| Catch rate | stats byte 8 | 29 |
| Sprite size | stats byte 10 | 0x88, claims 8 by 8 tiles, but the buffer holds 7 by 7 |
| Sprite location | stats bytes 11-12 | a pointer into data that is not a sprite |
Why the shape looks broken
That size byte is the source of MissingNo.'s jagged silhouette. It claims the sprite is 8 tiles wide, but the display space the game copies it into is only 7 tiles across. When the copy routine reaches the edge it wraps to the next row, one tile too soon, and the whole picture shears into the tall, hooked column players recognize. The shape is not a drawing. It is an off-by-one error, made visible.
The item multiplication
Encountering MissingNo. does one more famous thing. The moment the battle starts, the game increases the quantity of the sixth item in your bag by 128. It is a side effect of how the Pokedex tracks which creatures you have seen: MissingNo. flips a bit it should never touch, and that bit lands on your item count.
This is the reason so many players deliberately hunted MissingNo. despite the risk. Put your rarest, most valuable item in the sixth slot, meet MissingNo., and walk away with an army of them. Here the sixth slot, a single Rare Candy, has become a stack of 153. It was the closest thing Red and Blue had to a cheat code, hidden inside a monster.
How you actually summon it: the old man
MissingNo. is not lurking on that coast by accident of geography. It is conjured by your own name. When the old man in Viridian City shows you how to catch a Pokemon, the game temporarily overwrites part of its memory with his battle, including the strip of memory that decides which wild Pokemon appear where. Your name gets left sitting in that strip.
So when you fly to Cinnabar and surf the coast, the game reads the letters of your name as species numbers. Most names contain at least one letter that maps to an empty slot, and the empty slot is MissingNo. Different names summon different members of the family, which is why two players standing on the same tile could meet two completely different broken creatures. Your MissingNo. was, in a real sense, yours.
The Bird type
One of the strangest things MissingNo. exposes is a type that does not exist. Its primary type reads as Bird, a category present in the code of Red and Blue but cut from every real Pokemon before release. Flying was kept, Bird was abandoned, but the leftover slot in the type chart survived. MissingNo., reading raw bytes as a type, lands on it, making it one of the only creatures in the game to carry a type the designers deleted. A fossil of a decision, worn by a fossil of a Pokemon.
Across five cartridges
People say MissingNo. like it is one thing. It is not. I decoded the same empty slot from five different versions, and they disagree. Red and Blue share identical data. Yellow moved things around. And the two original Japanese carts, Red and Green, are different machines underneath, so the accident lands somewhere else entirely.
| Version | What changes |
|---|---|
| Red / Blue (US) | The canonical MissingNo. Identical data between the two, same behavior. Shown above in the purple palette a Super Game Boy assigns it. |
| Yellow | Different sprite data at the empty slot, so it comes out a different shape entirely, and on a Game Boy Color it inherits that red and yellow fire palette. That is my real Yellow encounter above, next to my Red one, and you can see they are not the same creature. |
| Red / Green (JP) | The originals. A smaller ROM with a differently shaped stats table, so the byte math lands on unrelated data. A different glitch entirely. |
The Japanese Red and Green cartridges are the true first drafts, released months before the game reached the west. Their glitch behavior is its own rabbit hole, and a future update to this page will decode their empty slots in the same detail. If you have a beta or prototype cartridge dump, I would genuinely love to add it.
Does it still work in 2026?
Yes. This is the part people are surprised by. Nintendo re-released Red and Blue on the Nintendo 3DS Virtual Console in 2016, and they shipped the glitch intact. The old man trick, the coastline encounter, the item duplication in the sixth bag slot, all of it still runs on a modern handheld you can buy today. The empty slot was never patched, because patching it would mean changing the game, and the whole point of a faithful re-release is that it is the same game, bugs and all.
| Where | Still works? |
|---|---|
| Original Game Boy cartridge | Yes. The source of everything on this page. |
| Game Boy Color / Super Game Boy | Yes, with the auto-palette you see in my captures above. |
| 3DS Virtual Console (2016 re-release) | Yes. Unpatched. The most accessible way to meet it in 2026. |
| Later remakes (FireRed, Let's Go, etc.) | No. Rebuilt engines, the empty slot no longer overflows the same way. |
January 11, 2026 was the glitch's twenty-seventh anniversary, and people spent it doing what I have done here: tracing where it comes from, arguing about which cartridge does what, and proving to themselves that the strangest thing in the game is still sitting there, one bad name away from appearing. Twenty-seven years is a long time for a mistake to keep working. That durability is the whole reason The Glitchhouse exists.
Hear it, synthesized from the cartridge
A Pokemon's cry is three bytes: a base sound, a pitch shift, and a length. The game reads those three bytes out of a table using the creature's index number. MissingNo. lands on a slot that gives it a base of zero with a pitch of zero and, crucially, a length of zero, so its cry comes out as a clipped, wrong-sounding stub of a sound that was never meant to play this short.
This is not a recording. I read MissingNo.'s three cry bytes from the ROM and rebuild the sound live in your browser from the Game Boy's own two pulse channels and its noise channel, the same way the hardware would. Press play.
My history with this thing
I have been GardenFlouer online since I was a kid, and glitch Pokemon are a big part of why. Here is MissingNo.'s cry, and, if the tape still exists, the video of a much younger me finding it for the first time.
The cry
The day I found it
Fight it yourself
This is my from-scratch recreation of the Red battle engine, not an emulator, running natively right here on the page. The enemy is preset to MissingNo., with its real Bird typing, its 136 attack and its zero defense. Pick your own fighter and see how a battle against the empty slot actually plays out.
Arrow keys move, Enter or Z is A, Escape or X is B. Or just tap the screen.
Every number and every sprite on this page was decoded from a Pokemon Red ROM by reproducing the game's own out-of-bounds reads. The compressed sprite pipeline, the stats, the type chart, the item logic, all of it comes from the cartridge. Part of The Glitchhouse, a field guide to the broken Pokemon of Red and Blue.