Nintendo is running their Pokemon Black and White Tour currently, and one of the attractions is the ability to download a special Pokemon to your copy of Pokemon Diamond, Pearl, Platinum, HeartGold, or SoulSilver, the Mythical Celebi… who I guess isn’t all that much of a myth if you can just download it.
However, the Pokemon Black & White Tour is only visiting a few cities over the next few weeks. So that Pokemon fans not near those locations won’t miss out on everything, Pokemon.com has announced that from February 21st through March 6th of this year, GameStop will be hosting the same Celebi download event that is accompanying the tour at all of their US locations.
Downloading Celebi and transferring it to Pokemon Black & White will allow you to meet (and capture) the Pokemon Zorua. That Pokemon is otherwise unavailable in the game.
This is an in-store only event. You must got to a US GameStop store during the dates listed to be able to download these Pokemon.
However, since it is an in-store event, you will be able to download these Pokemon to Diamond, Pearl, Platinum, HeartGold and SoulSilver.
As usual, all of the details are available at Pokemon.com.