Missingno.

Description
Representative of a side of the Pokémon world few dare to explore, Missingno is an enigma. Exceedingly rare, it has eluded even the most prestigious Pokémon researchers; as such, very little in the way of official information on it is available. Missingno. possesses immense strength which it can focus into its physical attacks. Despite lacking any semblance of limbs, Missingno. is capable of punching. It also possesses psychic powers. It took seven diferent forms, and appears because the game have a bug.

Volcanic islands are one's best bet for locating Missingno. They are commonly seen flying above the water's edge, though never actually in the water.

These are the different forms of missingno:

Location

 * Mystery Gift: sndgames

Shiny

 * Mystery Gift v6.3.1: 46233nc4

Shadow

 * Game Corner (Random Non-evolved Shadow Pokémon): 300,000 coins
 * Mystery Gift v6.5: s20r25o4

Trivia

 * Missingno. is one of the few Pokémon not listed in the Pokedex . The others are Entei, Raikou , Suicune , Celebi , Kyogre , Groudon , and Victini.
 * Missingno. is the only Pokémon that had all 3 varieties (Regular, Shiny, and Shadow) available via Mystery Gift.
 * The regular Missingno. is the only Pokémon that appears twice in the Mystery Gift codes
 * Missingno. is the final Mystery Gift available in the game.
 * Missingno. has the highest Attack Stat in the game, but has the lowest Defense Stat, Special Defense Stat and Special Attack Stat.