I may be wrong as well. I do know that originally, in Japan, there was a special Mew pokemon that people uploaded to your cartridge for buying your game at a convention or something like that. I'm sure Wikipedia has all the answers:
It DOESN'T!!!
* `M and Missingno.: An infamous glitch, occurring as a wild Pokémon encounter on Cinnabar or Seafoam coast after either talking to a certain man in Viridian City, or after trading with one of the traders in Cinnabar Island.[9]
* Cinnabar Coast Pokémon: By surfing up and down the east coast of Cinnabar Island, Pokémon that normally appear from the last place visited will appear here (including Safari Zone Pokémon, which the glitch is most commonly utilized for). Also, many odd Pokémon over level 100 and trainers with glitch Pokémon have been found on the coasts of Cinnabar and Seafoam Islands (these can be found by performing the Missingno trick, and the kind of Pokémon, level of the Pokémon, and how many different Pokémon can possibly be found depend the on player's name).
* Item Duplication: A side effect of meeting the Missingno. It causes the sixth item in the player's inventory to increase by 128.[9]
* "Mew Glitch": A glitch which, if properly performed, can trigger an encounter with a wild Pokémon of any species, most commonly utilized for Mew, a legitimate Pokémon normally available only through Nintendo promotional events.[10]
* Other Glitch Pokémon: There are many glitch Pokémon that can be found in the game using a Gameshark or the "Mew Glitch". Usually they have unusual names (for example: 4. 4).
* Glitch City: An area like a town or city, composed of scrambled background graphics. Created by a series of steps involving the 'timer' in the Safari Zone.[11]
* Walk Through Walls glitch: One must perform the Glitch City glitch, but when the timer runs out, one must be in midair from jumping over a ledge. When sent back to the Safari Zone's main building, the Trainer can walk through walls inside the building. If all the player's Pokémon are poisoned and they faint, the Trainer is sent outside the building and can walk through walls throughout the Pokémon world.
* "Invisible PC Glitch": In Celadon City, there is a hotel, which has a layout extremely similar to that of a Pokémon Center. At the far right of the hotel, if the player presses the A button at the location where the PC in the Pokémon Centers usually are, a PC is somehow activated.
However, this has it all:
http://bulbapedia.bulbagarden.net/wiki/Missingno.
