Verdict: Confirmed True · 1990s
MissingNo is a genuine glitch Pokémon in the original Red and Blue games — a real, catchable entity born from the game's memory management, famous for duplicating items and its strange, corrupted appearance.
MissingNo (short for "Missing Number") is a data glitch that results from the original Pokémon games' wild encounter algorithm reading uninitialized memory as Pokémon data. The encounter is triggered by a specific sequence of actions: speaking to the Old Man in Viridian City who teaches the catching tutorial, then flying to Cinnabar Island and surfing along its eastern coast. The game's encounter routine reads the player's name characters as Pokémon indices, and certain name characters map to non-existent Pokémon entries — MissingNo is the game's handling of this unrecognized index. Its most famous effect is multiplying the sixth item in the player's inventory, a consequence of MissingNo's catch triggering a routine that writes to the item count byte. MissingNo was documented in Nintendo Power and officially acknowledged by Nintendo, making it the rare urban legend that turned out to be entirely real.
MissingNo exists because of a specific interaction between Pokémon Red and Blue's wild encounter system and the game's player name storage. When the Old Man's catching tutorial plays, the game temporarily stores the player's name in the buffer normally used to store the enemy trainer's name. After the tutorial, this buffer is not always cleared correctly.
When the player surfs along Cinnabar's eastern coast, the wild encounter routine reads data from this buffer to determine what Pokémon to generate. The player's name characters are ASCII values that map to Pokémon indices. If those indices point to non-existent entries in the Pokémon data table, the game loads MissingNo — the placeholder entry that sits in those empty index positions.
The item duplication effect occurs because MissingNo's sprite data, being garbage data, happens to write to the memory address containing the count of the sixth inventory slot when the encounter routine processes the "catch" event. The result — a multiplied item — is genuinely useful to players and made MissingNo famous beyond the usual circle of glitch hunters.
MissingNo is unusual among gaming legends in that its confirmation as a real glitch made it more culturally significant, not less. Rather than deflating the mystery, the technical explanation added a new layer of fascination: the idea that a game's own code could generate an emergent entity from boundary-crossing data was genuinely exciting to a generation of players who were beginning to understand programming.
MissingNo became a symbol of the gap between a game's intended design and its actual execution — a reminder that software is a complex system capable of surprising its creators. It influenced subsequent gaming culture's fascination with glitches, speedrunning exploits, and the archaeology of game code. The Pokémon franchise's own relationship with MissingNo is complicated: the entity has never been officially incorporated into the games, but Nintendo's acknowledgment of it in Nintendo Power legitimized the phenomenon in a way unusual for corporate game design.