Trivia: (Spoiler) Strahm is killed by the walls of the final room crushing him. However, in the original script, rather than the walls crushing, the room was supposed to fill with water, thus mirroring that trap that nearly killed Strahm in the beginning of the movie. Due to practicality reasons, this idea was dropped, though it does explain the air-tubes coming of the glass box. (Which would have been for Strahm to breath.)
Trivia: Patrick Melton and Marcus Dunstan, the writers of both "Saw IV" and "Saw V", have a cameo in the flashback of Hoffman being kidnapped and meeting Jigsaw for the first time. When Hoffman is about to get on the elevator right before getting kidnapped, Dunstan is the second man to exit the elevator (he is in black and has a beard), right after the snobbish woman. Melton is the tall man who exits the elevator last before Hoffman enters.
Trivia: In the beginning of the movie, Seth's trap consists of a bladed pendulum swinging towards him. We are told Seth is also a criminal. Agent Strahm's trap consists of a room closing in towards him. These are elements of the story "The Pit & the Pendulum," written by Edgar Allan Poe, who is widely considered to be the father of the horror genre and detective genre, both of which are used heavily in the film. Another of Poe's stories, "The Murders in the Rue Morgue," is also similar to the film. Ashley is decapitated, while a character in the story suffers near-decapitation. The characters in this story are also in a room locked from the inside.
Trivia: Much like "Saw IV" containing some subtle parallels to the original, this film contains several parallels to "Saw II", in an effort by the writers to create a second-trilogy that rhymed with the original. Parallels include: -Both films feature a lead officer-type protagonist who seals their own fate by refusing to listen to the rules and giving into aggression and personal hate. (Detective Matthews/Agent Strahm) -Both films contain a B-storyline about a group of characters whose refusal to work together leads to several dying. (The Nerve-Gas House/Five-Will-Become-One storyline) -Both films spend much of their time delving into the backstory of the lead antagonist and how they came to be. (Jigsaw/Detective Hoffman.) -Both films include a nod to the bathroom from the original. (It appears on-screen in "Saw II", and the door outside of it is visible briefly in "Saw V") -Both films end up down in the underground passageways beneath of the nerve-gas house/bathroom.
Trivia: The elderly couple who notices Jill Tuck in the waiting room near the beginning are actually the parents of the film's casting director, and the receptionist in the scene is played by a receptionist who works for Twisted Pictures (which produces the "Saw" films) in real life.