Director Richard Linklater intended to film the Philip K. Dick novel "Ubik," but decided to film Dick's "A Scanner Darkly" instead after Wiley Wiggins, who played the main character in Linklater's film Waking Life (2001), suggested it to him.
When Arctor is going through the second phase of testing with the medical deputies, the laptop-like machine on which he is being tested is branded as V K mk1. V K stands for Voight Kampff, the test used in "Do Androids Dream of Electric Sheep" (a.k.a. "Blade Runner") by Philip K. Dick, where the test is used to measure the response time and the involuntary reaction of the pupil of the eye, in short, an emotional reaction to determine whether they are humans or androids.
The title is an appropriation of 1 Corinthians 13:12, which reads, in part: "For now we see through a glass darkly; but then, face to face: now I know in part; but then I shall know even as I am known."
In Arctor's kitchen there is a drawing of a head in a box next to the phrase "Time to thaw Walt out!". This is a reference to the urban legend that animator Walt Disney had himself cryogenically frozen.
Robert Downey Jr. wrote most of his lines down on post-it notes and scattered them around the set so he could read off them while filming a scene. The rotoscoping team simply animated over the notes to remove them from the film during post-production.
When Arctor sits on the stage waiting to give his speech to the Brown Bear Lodge, one of the images his scramble suit displays is Philip K. Dick. This is a clever reference to the novel, in which the scramble suit is said to show the likeness of its creator once in every several million permutations.
When Freck goes to the liquor store to buy wine, one of the brand names being advertised is St. Ubik. This is a reference to Philip K. Dick's novel "Ubik".
The brand on the earphone of the woman in the surveillance room reads »Phil D.«.
The brand on James' wrist calculator reads »Philip«.
The Red Pills known as Substance Death, a drug that alters a user's reality, bear a striking resemblance to the Red Pills given to the character Douglas Quaid in the film Total Recall (1990) that, in this instance, are used to bring Quaid out of the Rekall Memory Implant-induced reality.
The filmmakers looked at 60 houses before settling on the one used for Arctor's home.
Each minute of animation required 500 hours of work by 50 animators working full-time.
After the movie was shot, it was then edited and picture was locked before it arrived to the animators. Animators were in post-production for roughly a year and a half.
Philip K. Dick's daughters gave director Richard Linklater their father's personal copy of the novel "A Scanner Darkly" when he completed this movie.
According to director Richard Linklater, filming was completed in 23 days; the animation process took 18 months.