from an event or by trading
Special Event or (*cough*) cheats.
Go to a game stop event for obtaining Celibi
there is a Nintendo event maybe at gamestop and go to it with Pokemon heartgold and soulsilver and there you will get celibi
there was an event with celibi but it is over so you cant get him without a cheat code system called an action reply ds
You Cannot actually get Celibi on Either Colosseum or XD: Gale of Darkness, However you can Get Celibi on Pokemon HeartGold and SoulSilver. In Pokemon Colosseum if you use The Flute Thing that purifies Pokemon Celibi will come to Purify Your Shadow Pokemon. I'd Reccommend using it on Something like Metagross, Tyranitar or Raikou or something like that.
Find an event giving it away
you can either cheat e.g. R4 card or AR, or you receive it from a mystery gift event
Special Events, trade, and cheats.
you cant find celebi in soulsilver
Yes,but you have to get the gs ball by copleting your pokedex then go to vir dan city and receive it then go to Kurt the next day talk to Kurt again and go to the ilexforest shribe and celibi level 30 will attack.
Not right now, unless you find someone willing to trade. Remember, HeartGold and SoulSilver are coming out in 2010, and Celibi was introduced in Gold and Silver, so there's a good chance Nintendo will eventually re-release Celibi in another event. Keep an eye on www.pokemon.com
Only through Nintendo events, of which there are few at the moment.
Yes, you can. Every once in while you get a special gift from the internet (note you need WI-FI) and it might be Celibi or other rare Pokemon and shiny's like pikachu coloured pichu