Cast the Runner-Up: William Hurt was initially asked to play Dr Schreber, but ended up cast as Inspector Bumstead. Dr. Schreber himself was conceived as being an older man, but Alex Proyas felt that making the character younger gave him more reason to try and rebel.
The Cast Showoff: Although her voice was, for whatever strange reason, dubbed by Anita Kelsey in the theatrical version, that's really Jennifer Connelly singing at the jazz club in the director's cut, and she's really quite good at it.
Creator Backlash: Alex Proyas was dissatisfied with some of the effects, particularly the spiral that comes out of John's forehead when he's Tuning. This was fixed in the Director's Cut, which was made after special effects technology had evolved.
Dark Horse Casting: Rufus Sewell was cast because audiences were unfamiliar with him, as it's a mystery for the first half whether he should be trusted.
Viewers Are Morons, so we have to explain the plot in an Opening Narration so they don't get confused and scared. Thankfully excised in the Directors Cut (or just mute the sound for the first few minutes). Alex Proyas recalls it being the first time he was told to "dumb it down".
The movie was given an R rating by the MPAA mostly because it had a "weird" concept (there were a few shots of topless women, but their collective duration is very short). At least that's what they'd have you believe: according to Matt Stone and the documentary This Film Is Not Yet Rated, the MPAA is extremely unkind to independent features and will rate them as anything, whether or not they see fit. Before they were bought by Warner Bros.., New Line Cinema couldn't even get the MPAA to return their phone calls.
Extremely Lengthy Creation: Alex Proyas began writing the script in 1990, shortly before he directed The Crow. He admits some of the design and city aesthetic ideas were shared between the two projects. After that film was a hit, studios began asking him what he projects he had up his sleeve he wanted to work on.
Flip-Flop of God: There are two differing opinions between the director Alex Proyas and the co-writer David S Goyer. Proyas believes the humans are the inhabitants of an interstellar space ship that were abducted by the Strangers. Goyer on the other hand believes they're all actually dead and the city is a sort of purgatory for them.
Focus Group Ending: Test screening audiences were "troubled" by the notion that the entire city wasn't sucked out into space once the Shell City Wall was breached. Thus, a last minute SFX addition of Bumstead and a Stranger drifting through a force field was created.
Never Work with Children or Animals: Subverted! Despite apprehensions about the twin children playing Mr Sleep, they were apparently so enthusiastic to work on the film; both were also huge fans of Rocky Horror, and were in awe of working with Richard O'Brien.
Non-Singing Voice: Jennifer Connelly's singing is dubbed in the theatrical version, but her real voice is in the Director's Cut. If you listen to her voice in the director's cut, she sounds great, only slightly unpolished and without the vocal training of a proper pro singer. Which makes perfect sense; Emma Murdoch isn't a professional singer either, this is just the job the Strangers have most recently assigned her.
Prop Recycling: Several of the sets from this film were reused in The Matrix, most recognizably the corrugated rooftops seen during Trinity's run from the cops in the opening, and the staircase with the black-and-white tile floor from the SWAT raid and Morpheus' capture.
Alex Proyas says of those who suggest the Strangers parallel the Greek Gods manipulating mortals?
"I do like Greek mythology and have read a little of it, so maybe some of it has crept into the work, though I don't completely agree with that point of view."
He also says he prefers to keep it vague why the Strangers really set up the city - beyond "looking for the human soul" - feeling it made for a richer film.
The film was more about the impact they had as a result of that experiment on human beings, so if it begged for more answers then I always thought that was a good thing.
Unbuilt Casting Type: In one of his earlier roles, Rufus Sewell plays around with his later typecasting as villains - as it's left in doubt whether John Murdock is actually a serial killer. He's not and he's meant to be implanted with that persona.
Dr Schreber was first envisioned as an older man (and Keifer Sutherland assumed it was a mistake when the script was sent to him, thinking it was for his father instead). They opted to make the character younger to make him more tragic - as he had his whole life ahead of him.
An early draft of the script would have had Dr. Schreber getting skinned alive during the climax. The Strangers were also going to win, making for a complete Downer Ending in the process.
Another possible term for what the Strangers do was 'the occasion' (which the screenwriter preferred). They went with 'tuning' because it was a more obscure word and therefore sounded more alien.
Bumstead was the main character in the early draft - which revolved around a 1940s detective who goes insane trying to solve a case where the facts do not make sense. Alex Proyas felt it was better to set it from the perspective of the guy being chased instead. Some of Bumstead's original characterization made it into Walenski in the finished film.
The first draft of the script by Alex Proyas was vastly different from the finished film. It includes the appearance of the Strangers, the setting of a perennial Dark City, and the fact that John Murdoch is wanted for a series of murders that he does not recall committing. Notable aspects of the initial script include an evil robotic puppy accompanying the Strangers (which would attack savagely with its steel jaws) and a climactic trial for John Murdoch. The reanimated corpses of the victims would testify against Murdoch in the trial, and even John's wife would be a witness.
Alex Proyas has said that there are some scenes he would have liked to restore in the Director's Cut, but wasn't able to due to lack of resources. He has however said that the most important scenes have all been restored.
On the DVD Commentary, David S. Goyer reveals two possible explanations for the origin of the inhabitants of Dark City. In his original story outline, Alex Proyas believed the humans to have been passengers aboard an interstellar spaceship which was captured by the Strangers. Goyer favors a more spiritual approach, supposing that the humans are in fact dead and that Dark City is a sort of purgatory made up of people the Strangers have selected or abducted from different eras in history.
Alex Proyas says that the Strangers didn't get rid of Walenski earlier because he was an additional part of the experiment; to see how he would react, and people would react to him in turn.
Keep Circulating the Tapes: Not only is their first and only album hard to find, with the CD version going for rather high prices on auction sites, but their non-album singles are incredibly rare and only on LP, making them vulnerable to disc rot. In other words, good luck actually listening to this band.