The rarest of all pokemon, the elusive Celebi will arrive at Gamestop from February 27, - March 11, 2011.
AFAIK, there was no legitimate way to obtain Celebi outside of Japan (i.e. you need the Japanese version of the game or you need to trade over regular wireless or regular Wi-fi [NOT GTS] with someone who has the Japanese version of the game).
This is pretty much the pokemon that we've all been waiting for, ever since HeartGold and SoulSilver were announced.
According to Bulbapedia, the Celebi will be Level 50 in a Cherish Ball with a Classic Ribbon, holding a Jaboca Berry. The move set will be Leaf Storm, Recover, Nasty Plot, and Healing Wish. So it's essential just like the Japanese Movie Celebi.
According to Bulbapedia, Celebi will trigger an event in HeartGold and SoulSilver. Also, if Celebi is transferred to Pokemon Black and White, players can receiver Zorua in Castelia City.
Credit goes to Bulbapedia News, where I read it. Here is the link:
All 4th Generation pokemon games (Diamond, Pearl, Platinum, HeartGold & SoulSilver) will be able to download Celebi via Mystery Gift. As always, you need to have an open slot for your Mystery Gift, so start soft-resetting (I will be soft-resetting Ash's Pikachu).
I hope people will stop posting about being ashamed to enter Gamestop to download the Mystery Gift Wonder Card. The reality is ... no one you know will be there, and no one really cares. :)