MissingNo.

MissingNo. (; Japanese: , Hepburn: ) is a glitch and an unofficial Pokémon species found in the video games Pokémon Red and Blue. Due to the programming of certain in-game events, players can encounter MissingNo. via a glitch. It is commonly regarded as one of the most famous video game glitches of all time.

Encountering MissingNo. causes graphical anomalies and changes gameplay by increasing the number of items in the sixth entry of the player's inventory by 128. This beneficial effect resulted in the glitch's coverage by strategy guides and game magazines, while game publisher Nintendo warned that encountering the glitch may corrupt players' game data. IGN noted MissingNo.'s appearance in Pokémon Red and Blue was one of the most famous video game glitches and commented on its role in increasing the series' popularity. Fans have attempted to rationalize and incorporate MissingNo. as part of the games' canon as an actual in-game character, and sociologists have studied its impact on both players and gaming culture as a whole. Additionally, references to the glitch and the circumstances around it have also appeared in other games, such as Vampire Survivors and The Binding of Isaac: Rebirth.