The Big O (THE ビッグオー) is the title of an anime television series, which also has a manga adaptation. The Big O manga is published in English by Viz Communications. Both seasons of the anime series have been released on DVD by Bandai Entertainment. The Big O was written by Chiaki J. Konaka, who also wrote scripts for Bubble Gum Crisis, Magic Users Club, and Serial Experiments Lain. Producers were Sunrise and Cartoon Network (during second season).
The principal character of Big O is Roger Smith, a professional freelance negotiator, but the added twist on the show is the fact that he is also the pilot of Big O, an enigmatic giant robot known as a megadeus which is a creation from the world prior to "The Event". (Wikipedia)