Celebi did not originate from fanon, and the information on this page may not be entirely accurate to their canon. You may read more about this subject in the context of their canon on the following wiki(s):
Celebi is a Time/Grass-typePokémon, originating from Johto. It is the only one Mythical Pokémon of this region, and has the ability to travel through time.
Celebi is a green fairy-like Pokémon. It has round toeless feet, three-fingered hands, and clear wings on its back. It has a round head that comes to a curved point. It has large baby-blue eyes with thick black rings around them, and a pair of green antennae with blue tips.
Often found in forests, Celebi is a Legendary Pokémon, known in legend as the "Voice of the Forest." It is able to travel through time and exist simultaneously throughout time, and plant life flourishes wherever it has been. It is able to bring deceased Celebi back to life and restore plants to perfect health. Celebi also has the power to instantly cause the Purification of any Shadow Pokémon and can be summoned at Relic Forest with the melody of a Time Flute. Despite living in forests as its guardian, Celebi only shows itself in areas and times of peace. It has been regarded that as long as Celebi are seen throughout the world, a prosperous and bright future is still in store for the Pokémon World.
Also, this Celebi is the only Shiny Pokémon to appear in the Pokémon Mystery Dungeon series prior to the WiiWare games.
Although Celebi has a Shiny sprite, it has never been distributed as a Shiny.
A 2008 interview done with Masamitsu Hidaka revealed that the GS Ball was initially meant to contain a Celebi that would be used in a story arc throughout the Johto series. This idea was shelved, however, and Celebi became the star of Celebi: Voice of the Forest.
Celebi is the only Pokémon whose number in the National Pokédex and the New Pokédex are the same: 251.
Although Celebi has the power to purify any Shadow Pokémon in Pokémon Colosseum and Pokémon XD, trading Celebi to one of these games will not accelerate or complete the purification process.
Celebi follows the trend of every generation introducing a Legendary Pokémon with a base stat total of 600 and a stat distribution of 100 all around. Others that follow this trend include Mew, Jirachi, Manaphy, Land Forme Shaymin, and Victini.
According to a dead Nintendo of Japan page from the early 2000s, Celebi's Japanese name was initially romanized as Selbi as opposed to the later Celebi.
Celebi has a natural theme. Celebi might be related to nature worship of Shintoism. It may be based on a fairy, dryad, or kodama. Its fierce protectiveness for its forest home resembles that of the Curupira.
Celebi may be a combination of celestial and being, or it may be a combination of serenity and 美 bi (beauty).
Names in other Languages
From celestial, cerebral, celery, Cybele, serenity, being, and 美 bi (beauty).
Dream World Artwork
Celebi's Artwork from Pokemon Diamond & Pearl Anime