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Genres: action, mystery, psychological, science fiction
Themes: Mecha
Age rating: PG - Children

Plot Summary: Paradigm City is a place without a past. 40 years ago, something happened that wiped the memories of everyone in it. Unfortunately, the people of Paradigm City were very busy before then, making Megadueses(giant robots) and monsters. People who were born after the memory wipe are gaining/recovering memories of the past and using them to build newer threats. Roger Smith keeps Paradigm City safe with the help of The Big O (a faithful giant robot), his butler Norman and the android Dorothy, Roger keeps Paradigm City safe. As problems mount and more memories surface, Roger’s past and Paradigm’s future begin to become suspect…(Source: ANN)

Episodes: 26
Status: Finished Airing
Aired: Oct 13, 1999 to Mar 27, 2003

Opening Theme:
#1: “Stoning” by Toshihiko Sahashi (Eps 1-2,14)
#2: “Big-O!” by Rui Nagai (Eps 3-13)
#3: “Big-O!” by Rui Nagai [USA DVD Release] (eps 15-25)
#3: “Respect” by Toshihiko Sahashi (Eps 15-20,22-25)
#4: “Big-O! Show Must Go On” by Rui Nagai [2007 ANIMAX Broadcast]
Ending Theme:
“And Forever…” by Robbie Danzie with Naoki Takao
“Stand a Chance” by Toshihiko Sahashi [Cartoon Network Toonami Broadcast] (eps 1-13)