Briefly mentioned in the game's manual is a character named "Mr. Nasty". While Lionel Starkweather serves as the director for Valiant Video Enterprises, Mr. Nasty serves as the financial backer and producer, as well as the administrator for the company website's forum. This fictional forum was hosted on Manhunt's now-defunct website, and expanded on the backstory of Mr. Nasty through forum posts as he tried to maintain the exclusivity and financial security of the snuff film ring. One post he made on August 27, 2003 teases the events of the first level "Born Again" on November 19, which shares the North American release date of the game. His last post on the forum, posted about a month before the events of the game, is a bounty offer for the head of the Journalist after he learned of her probe into the company's affairs. Mr. Nasty's fate is left ambiguous at the end of the game, as the game's manual and website only reference the story up to the events of the 11th scene "Mouth of Madness".

During the scene "Press Coverage", there is a photograph of a man on the bedside dresser in the Journalist's apartment. This is a photo of asset artist Campbell-John Dick.

The game's manual is themed to resemble an in-universe home video catalog from Valiant Video Enterprises, featuring personal ads from Cerberus and a member of the Wardogs, and a list of previous Valiant releases such as "Piggsy's Greatest Hits" and "Let's Play: 'Ramirez Sez'".

During the final boss fight against Piggsy, his first appearance in the attic shows him bearing a fully modeled penis and testicles, but for unknown reasons, they disappear during later encounters.

During the scene "Press Coverage", inside of the Journalist's apartment, a calendar on the wall has the date of November 19th, 2003 marked with a smiley face doodle. This is the North American release date of the game itself, being a meta Easter Egg, and may also double as environmental storytelling; the Journalist may have been anticipating this date as being important in Spoiler:her independent investigations into Lionel Starkweather's snuff film ring.

A boss character by the name Binbag was removed from the game early in it's development. He was originally the leader of The Lost gang. It is stated in the bonus material that an early model for Binbag was made before he and The Lost were dropped from the game.

It is likely that Manhunt is set within the same universe as the Grand Theft Auto series, which are both published by Rockstar. There are multiple references to stores and locations in both games, and the setting for Manhunt, Carcer City, is directly referenced in multiple Grand Theft Auto games.

Manhunt was banned in several countries due to how violent it was.