From what American audiences have seen of the Pokémon franchise it hardly seems like it needs to be censored, but some major changes are made before anything Pokémon hits stores in the U.S.
Let's start with Jynx- in Japan this Pokémon is clearly drawn as a blackface caricature, and although Japanese audiences have never taken offense to the character they knew audiences in the U.S. would.
So what did they do to fix the problem?
They painted her purple, so now she looks like the Eggplant Wizard's wife instead of a minstrel show reject.
Pokémon cards have undergone a similar cleanup process to be sold in America, which meant removing anything which could be seen as controversial or inappropriate for kids.
So swastikas were removed from the Koga's Ninja Trick card, Misty's trainer card nudity was replaced with tears, and Grimer's pervy pupils were reoriented so he's no longer looking up some girl's skirt.
See 5 Weird Ways Pokémon Has Been Censored here (contains NSFW material)