to get a shedinja catch a nincada then make your party only have 5 pokemon.
then go to your pokemon party and press A on the captured nincada then go to summary on the first screen you should see the pokeball that you caught it with...,make sure that you have the same exact pokeball in your balls poket. Now raise your nincada to level 20 it will then evolve into a ninjadsk but go to your pokemon party and you will see a bronze type pokemon you now have a shedinja.......(shedinja s a good pokemon to have and this pokemon has the best effect out of all the pokemon in the game)
P.S.nincada is found on route 116