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 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 Issac.
History
Developed by Game Freak and published by Nintendo, the Pokémon series began in Japan in 1996 with the release of the Pokémon Red and Blue video games for the Game Boy. In these games, the player assumes the role of a Pokémon Trainer whose goal is to capture and train creatures called Pokémon. Players use the creatures' special abilities to combat other Pokémon, and certain abilities also grant new ways to navigate the game's world, such as instantaneous travel between two areas. The ultimate goal of the games is to complete the entries in the Pokémon index (Pokédex), a comprehensive Pokémon encyclopedia, by capturing, evolving, and trading to obtain creatures from all 151 Pokémon species.
MissingNo. is not an official Pokémon species that players are meant to encounter, but it is accessible to players in European and North American copies of the games via a glitch. Nintendo of America first documented the events that cause MissingNo. to appear in the May 1999 issue of Nintendo Power. The company warned that "any contact with it (even if you don't catch it) could easily erase your game file or disrupt your graphics". The glitch was not removed from the 2016 re-releases of Pokémon Red and Blue on the Nintendo 3DS Virtual Console, so players can still encounter MissingNo. in these versions of the games.
Characteristics
A player can encounter a MissingNo. in Pokémon Red and Blue by following a series of steps. First, the player watches an in-game tutorial for Pokémon capture in the game's Viridian City location. Second, the player uses a Pokémon with the "Fly" move to instantly travel to the game's Cinnabar Island location. Finally, the player uses a Pokémon with the "Surf" move to travel up and down on the eastern shore of the island until a MissingNo. appears.
These events manipulate the game's random encounter system to generate a Pokémon with an invalid identifier. Each area within the game assigns values to a data buffer to represent the Pokémon that can be encountered in that area. However, some areas—such as Cinnabar Island—do not overwrite the data in this buffer, so the data from the previous area is used instead. During the Viridian City in-game tutorial, the player character's name is temporarily overridden to read "OLD MAN", and the player character's actual name is temporarily copied to that same data buffer. If the player travels directly to Cinnabar Island after viewing this tutorial, the player character's name will be read as the Pokémon that can be randomly encountered in that area. Due to the player character's name not being intended to be read as this kind of data, the game can attempt to generate an encounter with a Pokémon with an invalid identifier, such as MissingNo. Fans have dubbed this method of encountering MissingNo. the "old man glitch".
As with any wild Pokémon, players may flee from, fight, or capture MissingNo. After an encounter with MissingNo., the quantity of the sixth item in the player's inventory is increased by 128, and the game's Hall of Fame Pokémon gallery becomes glitched. Temporary graphical glitches may also occur, which can be removed by viewing the statistics page for another non-glitched Pokémon or resetting the console.