Much mystery surrounds Pokémon's unofficial 152nd resident MissingNo, the unintended programming quirk which has become part of the games' mythology. Although this strange graphical glitch had the not-so-desired effect of wiping your save data, its elusive powers could also be harnessed to clone valuable items.
So, if you're willing to risk your game for a backpack brimming with master balls, follow the steps below and hunt down the legendary MissingNo.
1. After you've learnt to use Fly out of battle head to Viridian City.
2. Approach the old man in the north and ask to watch his demonstration of how to catch a Pokémon.
4. Return to Cinnabar island. Surf up and down the shoreline next to where the gym is.
5. After a while a MissingNo will appear. Warning: If you catch it it's likely to corrupt your save.
Note that after the encounter the sixth item in your bag will be duplicated 128 times, so make sure there's something juicy in there!
Would you go after MissingNo?