One would think that the Pokemon series is an unlikely candidate for any censoring because it is made especially for children. And despite some previous rumours about parallels to satanism or racism, there had never been any censoring involved. Until Pokémon Diamond/Pearl. In this version, one of the pokémons was altered a little.
In every following release, the altered sprite was used worldwide, which is why one can only speak of censoring in these two games.