Missingno (Pokemon)
"Missingno.", presumably for "missing number", is not so much a Pokemon as the result of a programming oversight in the Game Boy Pokemon game. Missingno is best known as the Pokemon responsible for:
- Screwing up your Pokemon cartridge if you mess with it;
- Allowing the (in)famous "Rare Candy Cheat";
Missingno. was a deliberate glitch added by the programmers of the game to aid them in testing. It allowed them to progress quickly by giving them access to many items straight away. It would appear that the beta version of the game had land paths to Cinnabar Island which were removed. The Box Trick would appear to be for the same reason.
So what's the mystique? Basically, Missingno. has acquired so much notoriety due to his presence in many of the Pokemon myths, especially involving Mew, the much-vaunted and non-present #151. While the myths aren't true, Mew's popularity ensures that Missingno. will always have a place in Pokemon culture.