- The name was changed from "The Sixth Day" to "The 6th Day" to avoid confusion with The Sixth Sense (1999).
- The Sim-Pal slogan is "A Sim-Pal that's fun to be with!", a derivation from "The Hitch-Hiker's Guide to the Galaxy" series by Douglas Adams. There, the corporation that created robots with "Genuine People Personalities" had the slogan "Your plastic pal that's fun to be with!".
- Christopher Lawford, who plays a police officer in the film, is Arnold Schwarzenegger's cousin by marriage.
- When Adam is locked in the room at the police station, the name of the webcaster appears on the screen as Marianne Wibberley. Wibberley co-wrote the movie with her husband Cormac Wibberley.
- The professional football league that Johnny Phoenix plays for, the XFL, was created in 2000 by WWE Owner Vince McMahon. It only lasted one season.
- Actor Trademark: [Arnold Schwarzenegger] I might be back.
- According to Arnold Schwarzenegger in the DVD featurette 'The Future is Coming', this movie is set in the year 2015.
- Kevin Costner turned down the lead role in this film due to scheduling conflicts with another film.
- The incendiary powder Adam makes is never named specifically, but based on its properties and ingredients, it appears to be thermite. The fact that Adam subsequently conceals thermite in a Thermos may be an in-joke from the filmmakers.
>>> WARNING: Here Be Spoilers <<<
Trivia items below here contain information that may give away important plot points. You may not want to read any further if you've not already seen this title.
- SPOILER: The Coliseum-like building that houses the genetic lab and is blown up at the end is actually the Vancouver Public Library.
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