Pokemon LeafGreen Hints

To get pokemon on the pokedex that isnt in kanto dex just have another firered or leaf green with the natonal dex an trade.

Its true that you can battle/catch missingno with gameshark.
but now,you can catch missingno. with only your gameboy!!!

first,go to viridian city.then,talk to the old man that will teach you how to catch a pokemon.allow him to teach you then go to cinnabar island.surf at thw water beside the volcano(badge)gym.put rarecandy/nugget or anything that you want to duplicate in the sixth place in your bag.you will encounter starmie/marowak level 180,electrode/snorlax level 146,MISSINGNO LVL 80 or lvl 0.WAIT!!!DO NOT CATCH THAT GLITCH POKEMON!!!
if you catch missingno,it will abuse your game.you CANT select the "NEW GAME" in your pokemon red/blue.missingno is like a "HACKED POKEMON" because you cant understand his face.it will also BROKE your "HALL OF FAME",but DONT WORRY.you STILL have a record of hall of fame but it is only broken.i hope i helped!!!