To the left of Black City/White Forest in your Black/White version, there is a building called the PokéTransfer or something along those lines. Here, you can send over Pokémon from Diamond/Pearl/Platinum/HeartGold/SoulSilver as long as they don't know a HM Move. You also can't transfer items in this way.
You need two DSes to do this.
UK VGC 2009 - Top 32
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