Defeat the Pirate Ganzack! was the first animated adaptation of One Piece, an original video animation (OVA) produced by Production I.G. It was originally released in summer of 1998, with a limited screening across Japanese theaters.
As it predates the “official” Toei anime, this OVA features markedly different animation and voice actors. It also does not adapt or reference any specific story from the manga, though its status quo vaguely fits the period between the Orange Town Arc and the Syrup Village Arc.