How to Clone Items on "Pokemon: Yellow Version"by Sam Orr ; Updated September 22, 2017
The first generation of the Pokemon series consists of "Pokemon Red," "Pokemon Blue," and "Pokemon Yellow," all of which follow the same basic plot through the same world. Because of this, these first-generation games have a glitch that allows players to duplicate items in their inventory to become formidable players, quickly increasing the power of their Pokemon, catching wild Pokemon with ease, and making a fortune almost instantly.
Move the item you want to duplicate to the sixth slot down in your inventory. The sixth item is the only one to duplicate when taking advantage of the glitch.
Speak with the "Viridian City" man at the north of the village, in a direct lineup from the entrance. Accept his offer to learn how to catch a Pokemon.
Access your list of Pokemon from the "Pause" menu and select one with the fly ability, then choose its "Fly" ability. Select "Cinnabar Island" as the region to which you want to fly.
Walk to the eastern shoreline of the island a short distance away from your starting location and use a Pokemon's "Surf" ability to move up and down the coast until you encounter the "MissingNo" Pokemon. "MissingNo" is a shortened version of "Missing Number," because the appearance of "MissingNo" indicates that the game cannot find which numbered Pokemon the battle is encountering.
Escape from the fight either by fleeing, capturing "MissingNo," or defeating him in a fight.
If you encounter a level 80 "MissingNo," capture it with a "Master Ball" and give it a rare candy to force it to evolve into "Kangaskhan," an extremely difficult Pokemon to find and catch.
Attempting to fight a "MissingNo" that is a level zero will freeze up your game.