The first season of the series premiered on 13 October 1999 on WOWOW with the episode "Roger the Negotiator" and concluded with "R.D." on 19 January 2000. Starting on 2 April, The Big O aired two times on the Cartoon Network: once during the afternoon Toonami block at 5:30 PM, and once at 12:30 AM during Toonami: Midnight Run; the 12:30 AM showing was the premiere and the more publicized 5:30 PM showing a rerun. Even at its late hour, The Big O was shown in edited form. In anticipation of the premiere of The Big O: Season Two, the first thirteen episodes were re-aired, completely un-cut, on the Adult Swim block.