9-Volt is a major character in the WarioWare series. He is a Nintendo fan, collecting everything relating to it, and loves to play video games. 9-Volt lives with his mother, 5-Volt, and his pet Fronk in their house in Diamond City. and attends Diamond City Elementary. He debuts in WarioWare, Inc.: Mega Microgame$!.
Since WarioWare: Twisted!, 9-Volt always stars together with 18-Volt in the WarioWare series, who becomes one of his best friends in this game.