I just got traded a pokemon but it had this wierd purple box that said PKRS what dose it mean?
PKRS is an acronym for 'Pokemon Virus', or PokeRus for short. It is a disease that may look bad, but is actually a good thing. You can catch PKRS off wild Pokemon, though there is a very low chance of that happening. The person you got the Pokemon off must have been lucky enough to ecounted a Pokemon with this status and caught the status off it.
PKRS = PokeRus
Read these links if you do not know what PokeRus is:
pokerus is a virus that doubles the evs you get in a battle.
if you do not know what evs are check out this link http://pokemondb.net/ev