Glitch Pokémon
What is MissingNo.?
MissingNo. is the most famous glitch in Pokémon Red and Blue: a scrambled, not-quite-a-Pokémon that was never meant to be seen.
The short version
MissingNo. (short for "Missing Number") is what the Kanto games show when they are asked to display a Pokémon slot that has no species behind it. The result is a garbled block of a sprite, a placeholder name, and stats that make no sense. It is not a hidden Pokémon, a secret evolution or a designed creature.
Why does it exist?
Red and Blue store Pokémon in a numbered list, and not every number has a species. A few small gaps are left over from development, and the list also contains spaces that were never given a name. If the game can be nudged into reading one of those empty slots, it still tries to build a Pokémon from it. The garbled picture and the odd name are what comes out.
The best-known way to reach it involved the game's wild encounter data being read from the wrong place after a particular sequence of moves. That is a bug, not a feature, and it is the reason this page does not give a how-to.
A short history
Players found MissingNo. soon after the games were released in 1998 and 1999, and it spread by word of mouth and early fan sites. It became famous for two reasons: it looks wrong, and it was said to do strange things to a save file. It has since been referenced in fan art, speedrunning and discussions of how the game works under the hood, and it remains a reminder of how much of a cartridge game's behaviour can be reached by accident.
Warning: it can damage a save
Meeting a glitch Pokémon is a way of making the game read data it was never meant to. Well-known side effects include a corrupted Hall of Fame record and a scrambled item count, and other problems are possible. If you want to see one, use a spare copy of the game or an emulator save you do not mind losing. Never try it on a save you care about.
Other glitch Pokémon
MissingNo. has relatives, such as 'M, which come from similar glitches. They get less attention, but they carry the same kind of risk.
Does it count in your Pokédex?
No. The Kanto Pokédex has 151 Pokémon, and MissingNo. is not one of them. In the Team Respawn tracker it lives in its own Glitch section on the Other tab, with a "Seen it" tick that is saved with the rest of your progress and does not change your percentage.
Questions
What is MissingNo.?
MissingNo. is a glitch Pokémon from Pokémon Red and Blue. It is not a designed Pokémon. It appears when the game reads a Pokémon slot that has no species behind it, so it shows a scrambled sprite and a placeholder name.
Is MissingNo. a real Pokémon?
No. It has no Pokédex entry and was never meant to be seen. Players found it shortly after the games came out, and it has been part of Pokémon folklore ever since.
Does MissingNo. count in the 151 Pokédex?
No. The Kanto Pokédex has 151 Pokémon. MissingNo. is not one of them, so the Team Respawn tracker keeps a separate "Seen it" tick for it and leaves your 151 progress alone.
Can MissingNo. damage my save file?
It can. Famous side effects include corrupting the Hall of Fame record and scrambling an item count. If you ever try a glitch like this, do it on a spare copy and not a save you care about.
Why is it called MissingNo.?
It is short for "Missing Number". The name is a placeholder the game shows when a slot has no real species data.
How do I track MissingNo. in the Team Respawn tracker?
Open the Pokémon Red, Blue and Yellow tracker, go to the Other tab and use the "Seen it" button in the Glitch section.