From Bulbapedia, the community-driven Pokémon encyclopedia.
Butch (Japanese: コサブロウ Kosaburō; Botch, コサンジ Kosanji (mistake)) is one half of of the Team Rocket duo that occasionally runs across Ash Ketchum and friends in the Pokémon anime. His voice actor is Eric Stuart (in the 4kids dub) and Jimmy Zoppi (in the Pokémon USA/TAJ Productions dub) in English and 子安武人 Takehito Koyasu in Japanese. Butch's dub voice seems to be an impression of Harvey Fierstein.
Butch's partner is Cassidy, and she is one of the few that usually manages to get his name right- much to his frustration, everyone else calls him either "Biff", "Bill", "Bob", "Hutch", "Butcher", "Patch", or "Botch" (コサンジ Kosanji in Japanese). Sometimes when she gets it right, he, by habit, tries to correct her and ends up calling himself the incorrect name. Everyone getting his name wrong has become a running gag in the anime.
Butch is named after Butch Cassidy, an American outlaw. His Japanese name, Kosaburo, is meant to diminish his status when compared to James. 二郎 Jirō is a name meaning "second son," while 三郎 Saburō means "third son." Kojiro (James) takes advantage of Jirō, while Kosaburo takes advantage of Saburō.