Pokemon Black - Pokemon Shifter - Got Use To It!!!This is a video of the Pokemon DPPtHGSS to BW trading system. BW sends a Pokemon catapult minigame over Download Play, which reads any inserted Gen IV Pokemon game and lets you attempt to transfer six Pokemon at a time. Any Pokemon you catch in the mini-game may be transferred to BW, and the rest are left in the Gen IV cart.
Trading is one-way, and does not allow Pokemon with held items (they'll be greyed out). It's region locked, or at least language locked. There's no daily limit. According to the video description, Pokemon with HM moves can't be traded either, and any uses of PP Up are reset. Ribbons are supposedly kept.
The PokéShifter is unlocked after beating the Elite Four and receiving the National Dex. Another feature, the Transfer Machine, allows trading Celebi and the shiny legendary dogs. It has the advantage of being available earlier. There's no Pal Park for Gen III games.