i.0. Chicago was founded in the 1980s by Del Close and Charna Halpern. The i.O. approaches improvisation as an art form in and of itself; this differs from the Second City approach, where improv is used as a tool in creating sketch comedy. i.O. also concentrates on "long-form" improvisational structures, in contrast to the "short-form" or "improv game" format of Theatresports or the television show Whose Line Is It Anyway?. The i.O.'s signature piece is the "Harold". ( The Harold is a form of improvised long-form comedy).