Plus there are limitations as well. You can't use a pokemon if its already being used by someone else for that type. Like say you want to use Lucario for fighting but someone else has that means you can only use it if you do steel. Check out the thread its in the Diamond/Pearl/Platinum chat forum
A monotype, generation duo challenge. You pick two pokemon of a single type(duals allowed) and they have to only be from one of the generations so like if you pick say generation two and want to do electric you can't have Pikachu or Raichu since they are gen 1. I picked Dragon from gen 3 and am going to use Flygon and Salamence.