MissingNo.
Once encountered, players can fight, flee, or capture MissingNo. just like any other wild Pokémon in the game. After encountering the MissingNo., the sixth item's quantity in the player's item menu will be multiplied by 128, and the game's "Hall of Fame" gallery might become damaged forever. Other display problems may happen, though these can be fixed by viewing a Pokédex entry or resetting the Game Boy. It commonly appears as a scrambled "d" shaped rectangle, though sometimes (encounter values) it will look like a Ghost or two fossils.