So, get a nincada, get it to level 20. Make sure you only have 5 or less pokemon in your party (including your nincada). Let nincada evolve into ninjask (get it to level 20) and look at your party, A SHEDINJA!!! (Have a normal pokeball in your pokeballs pocket for this to work)

if youb don't know how to get evolutions go to pokemon.marriland.com
and look around the web site until you see a link that say pokedex click
on it and u will get to how to evolve pkmn and how to get them.
(ps i think you get it when nincada evolves and it apears in a poke ball).

Train a nincada to lvl 20. Make sure u have a empty space on your team and have a spare pokeball. Check your party and u shoud have Shedinja.

just smell ur penis