2 definitions by National Pocket Monsters Research Society

An unused block of data in the Game Boy games Pokémon Red Version and Green Version in Japan. (later upgraded into a summarized game called Pokémon Blue Version, which had its code changed slightly and shipped to North America as Pokémon Red Version and Blue Version) The data is read by the game as a Pokémon named MissingNo., or "Missing Number." Apparently used as possible beta testing material or a scrapped idea. A hole in the game data was discovered allowing people to find it in the wild and capture it, causing major glitches and programming errors in the game's coding. It is supposedly Pokémon number 000 in the National Pocket Monsters Index, but is not officially classified.

This soon became the most popular name for any "glitch" Pokémon data found in later games in the series. When Pokémon Yellow Version, the sequel to Red and Blue versions, was released, MissingNo. was not found in the data, and was locked out of the previous games from trading and battling. In the games Pokémon Gold Version and Silver Version, blocks of unused data were found via hacking with cheat devices, but froze the game at certain points. Similar data was found in Crystal Version, the sequel to Gold and Silver Versions, but it all had no use.

When Pokémon arrived on the Game Boy Advance under the titles Pokémon Ruby Version and Sapphire Version, people began hacking the near-perfect coding to find unused or glitched data in the game. Indeed, one such block of data was found. It was Pokémon data labeled "?" and had its own sprites, stats, moveset, and National PokéDex number of 390. It functioned properly as an actual Pokémon And was tradeable. Obviously it was there on purpose, but most suspect it is merely for beta testing, as it had very basic attributes.

When remakes of Red and Green Versions, Pokémon FireRed Version and LeafGreen Version, were released, the very same "?" from Ruby and Sapphire Versions was found in the game data, registered under the same number and stats. It is fully usable once hacked out of the game data, and is tradeable with Ruby and Sapphire Versions. The purpose is still unknown.

The sequel to Ruby and Sapphire Versions, called Pokémon Emerald Version, upgraded from Ruby and Sapphire Versions much like Crystal Version did to Gold and Silver Versions. The "?" has been discovered to be tradeable to it and the same data is stored in the previous GBA games is still in Emerald Version. Nobody knows Game Freak's plan for this data. Perhaps it was merely a beta test and kept in later games for compatability purposes.
Contrary to popular belief, the original "glitch" data for MissingNo. in Pokémon Red and Blue Versions is NOT in the remakes Pokémon FireRed or LeafGreen Versions. The data has since been perfected.
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Rayquaza is the English name for a Pokémon originally named "Rekkuzza" in Japan. The English name was assigned by Nintendo of America.
In Hoenn, an island region in the Pokémon world, legend states that this creature, the "Master of the Skies," once descended from the clouds to end a cataclysmic battle between the Earth Titan "Groudon" and the Sea Titan "Kyogre." Occording to legend, the battle almost destroyed the earth. Had Rayquaza not ended the fight, all would be lost.
Thousands of years later, Rayquaza laid to rest atop a tall tower built long ago known as "Sky Pillar." It slept for years until a young child came and awoke it once more, as the evil organizations Team Magma and Team Aqua had called forth the Titans of Earth and Sea once more, not knowing if the consequences.
Upon being awakened, Rayquaza immediately flew to Sootopolis Mountain, modernly hollowed into a city and named Sootopolis City. This was where the Titans were clashing, much to the awe and fear of the local residents. Rayquaza repeated history and sent them back into their hidden caves, where they were to sleep peacefully forever more.
Rayquaza has since been captured and exact statistics on this respectable beast have been recorded in the Pocket Monsters Index, or the PokéDex.
Rayquaza measures in at a hight of 23 feet exactly, but only when sitting in a snake-like curl. Its long body from nose to tail has not yet been recorded, but is estimated to be about 60 feet or more. It weighs in at 455.2 lbs. It has the ability to pressurize the atmosphere around it, and nullifies all weather effects such as rain or intense sunrays. How it does this is yet to be explored. It is classified as Pokémon number 384 in the National PokéDex. It goes by the number of 200 amongst the Hoenn Region PokéDex. It has been dubbed the "Sky High Pokémon," for its ability to live in altitudes as high as the ozone layer.

A truely magnificent and rare beast indeed. There is only one in existance, but scientists in the Cinnibar Genetic Research Association are trying to clone it, so we may see more of this magnificent creature before the only one in existance dies.
The current owner of the one registered Rayquaza has asked to keep their information classified.
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