Bill is a Pokémon Researcher, widely regarded as an expert in many fields. He has made many appearances in the games. Bill is most commonly found in his Sea Cottage, which is north of Cerulean City at the end of Route 25. He is most notable for his first appearance in the Generation I games Red, Green, Blue, and Yellow versions and for his Pokémon storage system that has been pertinent in the entire main series.
In The Games
Bill is the talented and famous inventor. He invented the original Pokémon storage system and Time Capsule.
People, including himself, call him a Pokémaniac because of his large collection of both common and rare Pokémon. The first one he caught was an Abra; however, his favorite Pokémon are Eevee and its evolutions. Bill also gives a free Eevee to Ethan/Kris/Lyra in Generation II and its remakes and another one to Bebe in Generation IV, which is later given to Lucas/Dawn.
Bill also has several friends that share his interests in computer technology. One of them is Celio, his old friend from One Island in the Sevii Islands. He is also close with Lanette and Bebe, the storage system developers of Hoenn and Sinnoh, respectively.
Bill also has some fans, like PokéManiac Brent of Generation II who calls the player with information about him. Most of his calls are trivia about Bill himself and his family, such as the fact that Bill's mother used to be a Kimono Girl and that Bill's younger sister can't wink. Brent also revealed the fact that Bill is lactose-intolerant, which was also stated by Celio in Generation III.
Bill has been shown to have a large family. In Fuchsia City lives his adult sister and grandpa, who in Generation II watches over Bill's cottage on Route 25 while he is visiting the rest of his family in Goldenrod City.
In The Anime
Bill had previously been trapped in a Kabuto costume for what he claims to have been hours (in the dub only; the original didn't state how long he had been in the costume) until Ash finally comes to press the release button for him. Afterwards, Bill fulfills a request made by Professor Oak to give Ash and his friends a lesson on the basics of Pokémon, during which Bill shares the idea that there may be many more than just 150 species of Pokémon. The remainder of his appearance is spent focused on explaining to Ash and company his recent project, involving a mysterious Pokémon whose cry can be heard across the sea.
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