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Friend codes confirmed compatible between languages
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According to the official Japanese Pokémon Web site, trade via the Global Trade Station between U.S. and Japanese versions of Pokémon Diamond and Pearl will be possible. Players will be able to determine the location of the original trainer of each Pokémon, and traded Pokémon will retain their nicknames in full. As previously discovered, a subset of such foreign Pokémon will unlock foreign Pokédex entries: Ekans, Pikachu, Psyduck, Ponyta, Staryu, Magikarp, Wobbuffet, Heracross, Sneasel, Teddiursa, Wingull, Slakoth and Roselia traded from English, French, Italian, German or Portuguese versions have corresponding Pokédex entries in the Japanese version. This feature of the Pokédex may need to be unlocked by visiting a Hiker on Route 226.
Additionally, the globe in the GTS will be upgraded so that the world map is accessible, though this will only happen if the player trades with a foreign version of the game. It is not clear whether direct trading with a foreign version over Nintendo Wi-Fi Connection or over Wireless Communication is sufficient to unlock the world map. The site says foreign Pokémon will gain experience at an even faster rate than domestic traded Pokémon.