Question

What's an event celebi?

Answer 1

An event is basically where Nintendo officially releases a promotion where you can get special Pokémon and items and something like that. The event celebi is one of their promotions, and the promotions usually last for a little while. Most of the Pokémon are rare, or have special moves or items and my have a special use. If you relocate the celebi to your black and white game, you can get a zorua in castelia.

Hope this helps!

Answer 2

It's a Celebi given out in a special event. There have been a lot given out, and you can find a list of them on Bulbapedia. Some of them are given out at certain game stores, and others are obtainable anywhere.