MissingNo. 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. 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.