This trick allows you to fight Pokimon from the last area in which you areable to fight Pokimon (e.g. Unknown Dungeon and Safari Zone) All you have to do is go to the area in which you want to fight the Pokimon. You must have learned FLY and SURF. FLY to Cinnibar Island or the Seafoam Islands and SURF along the area in which it looks like you are on half-land, half-water. SURF up and down until you run into some Pokimon. They should be the Pokimon from the area you were last at. It makes it much easier to catch Pinsir and Scyther, even though you can buy them at the Game Corner.
This code is good for many things. Ok. Have Pokemon that know FLY and SURF. FLY to Viridian City and talk to the old man who would not let you pass at the beginning of the game. Answer NO to his question and let him teach you how to catch a pokemon. Then, FLY DIRECTLY to Cinnabar Island. When you land, go to your item list. Take whichever item you want duplicated and put it in the 6th spot from the top (it must have numbers next to it; GREAT EXAMPLES: Masterballs, Rare Candies, and PP Ups. NOT POKEFLUTE or other such items). Now, SURF up and down the right coast of the island so it looks like you are on half land, half water. You may run into Pokemon over 100. Eventually you will find a Missingno. Fight it and defeat it(it should be fairly easy). Immediately after, look at your item list. There should be 2 symbols where the numbers used to be. There are exactly 129 of that item. Now use this cheat with rare candies. Catch the pokemon above level 100. DO NOT USE THEM IN BATTLES AGAINST POKEMON IN THE GAME, ONLY AGAINST FRIENDS. They will level down to 0 if you do. Instead, use rare candies on them. They only go as high as 255, but it is well worth it! ENJOY!