From Bulbapedia, the community-driven Pokémon encyclopedia.
Celebi (Japanese: セレビィ Celebi) was a main character in Pokémon 4Ever. Its voice actress is Kazuko Sugiyama.
While trying to escape from a Pokémon hunter, Celebi stumbled across Sammy Oak, who was out looking for Pokémon. Just as the hunter was about to capture the Pokémon, it Teleported with Oak and ended up in the time of Ash and Ash's friends.
However, there was still danger in the present, this time from a Team Rocket member named Vicious. Using a Dark Ball, Vicious captured Celebi to use for his own evil plans. With the help of Ash and the others, Celebi was set free from Vicious. However, it looked very grim for Celebi, who wasn't able to heal itself in the lake where it had healed before.
Fortunately, many other Celebi from the past and future came to heal their friend. Once Celebi was healed, it was able to go back to the past and bring Sammy with it.
Related articles
For more information on this Pokémon's species, see Celebi.
