Paranoia Agent (妄想代理人 Mōsō Moso Dairinin) is a Japanese anime television miniseries about a social phenomenon in Musashino, Tokyo caused by a juvenile serial assailant named Lil' Slugger (Shonen Bat, or Bat Boy in the original Japanese version). The plot relays between a large cast of people affected in some way by the phenomenon; usually Lil' Slugger's victims or the detectives assigned to apprehend him. As each character becomes the focus of the story, disturbing details are revealed about their secret lives and the truth about Lil' Slugger.

It was created by Japanese director Satoshi Kon and produced by Madhouse.

The series first aired on Japan's WOWOW between February 2, 2004 and May 18, 2004. A series of four English dubbed and subtitled DVDs produced by New Generation Pictures were released in North America and Europe between October 26, 2004 and May 10, 2005 distributed by Geneon. A UMD version of Volume 1 was made available on October 10, 2005. The English dubbed version began airing in North America on Cartoon Network's Adult Swim on May 28, 2005 followed by an encore airing that began on June 6, 2006.

During the makings of his previous three films (Perfect Blue, Millennium Actress, and Tokyo Godfathers), Paranoia Agent creator Satoshi Kon was left with an abundance of unused ideas for stories and arrangements that he felt were good but did not fit into any of his projects. Not wanting to waste the material, he decided to recycle it into a dynamic TV series in which his experimental ideas could be utilized.

"In the case of a film to be shown at theatres, I'm working for two years and a half, always in the same mood and with the same method. I wanted to do something that allows me to be more flexible, to realize instantly what flashes across my mind. I was also aiming at a sort of entertaining variation, so I decided to go for a TV series."

An elementary school boy on inline skates dubbed Lil' Slugger (Shonen Bat in Japanese, meaning "Bat Boy") is said to be responsible for a series of mysterious street assaults in Tokyo. None of the victims can recall the boy's face and only two distinct details are left in their memories: golden inline skates and the weapon: a bent golden baseball bat.

Two police detectives, Keiichi Ikari and Mitsuhiro Maniwa, are assigned to the case to track down the perpetrator and put an end to his crimes. Starting with the first victim, Tsukiko Sagi, a shy character designer who created the immensely popular pink dog Maromi, the detectives follow what little clues they have and try to apprehend the mysterious boy. Just when they think they have solved the case, new evidence about the attacker leads them towards a frightening revelation.

Symbolism plays a vital part in the revelation of the plot, both on the episodic level and in the series overall, a better understanding of which provides more insight into the characters and the story for the original Japanese audience, but to a lesser exent for those unfamiliar with Japanese folklore and mythology. The series' ambiguous ending is a source of enthusiastic debate among fans.

The title of the show also plays heavily into the series. An example of this would be the paranoia that Yuichi feels towards Ushii in Episode 2. He believes that Ushii has been running a smear campaign against him.

Satoshi Kon is famous for his use of social commentary and Paranoia Agent is no exception (e.g., baseball bat related crimes in Japan). Commentary on his views of school peer pressure, loss of identity, prevalence of cultural icons (such as Maromi, often seen as a criticism of highly marketable anime mascots such as the poring from Ragnarok Online), ambiguity of morality, nature of social and personal growth, criticism of the harsh conditions of Japanese animators, and criticism of the otaku subculture is found throughout the show. Much of the commentary can be tied to Takashi Murakami's superflat manifesto, with the views of how reality and fantasy are being blurred in postwar Japan. Kon has been critically acclaimed for making social commentary a major and effective part of his work.

- From Wikipedia