Bill Paxton was almost cast as Peyton Westlake. According to Paxton, he told his friend Liam Neeson about the audition. When Neeson got the the role, Paxton was so angry that he did not speak to Neeson for months.
For the role of Darkman, Sam Raimi wanted someone who could play a monster with the soul of a man. An actor who could do all that beneath a lot of makeup. He also liked Liam Neeson's Gary Cooper charisma. Neeson was drawn to the operatic nature of the story and the inner turmoil of the character. To research the role, Neeson contacted the Phoenix Society, an organization that helps accident victims with severe disfigurements adjust to re-entering society.
Liam Neeson worked 18 hour days in ten-piece makeup, but he liked the challenge, and the idea of working behind a mask on camera, as well as exploring the possibilities this entailed. Neeson also had input on the costume he wore as Darkman, especially the cloak. The hardest part was speaking with false teeth, because he didn't want them to move at all.
Danny Elfman thoroughly enjoyed working with Sam Raimi on this movie. He commented "Sam has a wonderful visual style that lends itself easily to music. There was no reason to hold back on this one." The two would collaborate on future projects, but they're partnership ended with Spider-Man 2 (2004), due to creative differences. They would reunite however, for Oz the Great and Powerful (2013)
The editing process was extremely difficult, and the editor allegedly had a nervous breakdown and left production. The Universal executives were also rather nervous with some of the wild things in the film and insisted they be taken out. Sam Raimi confessed that studio movie-making, as opposed to independent filmmaking, didn't fulfill him in the same way. Raimi attributed Universal's marketing campaign to Darkman's success at the box-office.
The script went through 12 drafts overall. The reason is because Sam Raimi wanted to explore Peyton/Darkman's arc over the course of the film. He said: "I decided to explore a man's soul. In the beginning, a sympathetic, sincere man. In the middle, a vengeful man committing heinous acts against his enemies. And in the end, a man full of self-hatred for what he's become, who must drift off into the night, into a world apart from everyone he knows and all the things he loves."
The production suffered from behind-the-scenes troubles. The screenwriting process was grueling, and there were lengthy post-production battles with the studio. Also, Sam Raimi and Frances McDormand clashed because of creative differences. She was allegedly very difficult to direct. Raimi said, "apparently I didn't know Fran as well as I thought I did ... The reason it was difficult was that our conception of the best movie to make differed, arguing in trying to make the best picture possible. We did come across disagreements, but they were very healthy."
Larry Drake was cast because of the way he underplayed Durant. Quiet, careful, but intense. Sam Raimi had never watched a single episode of L.A. Law (1986), where Drake played the developmentally disabled Benny. But Drake's face reminded him of a modern day Edward G. Robinson. He looked so mean and domineering, yet he had an urban wit about him. Raimi believed these qualities made him the perfect adversary for Darkman.
Durant's finger fetish derived from Sam Raimi wanting the character to have a specific trademark - one that hinted at a military background, which would explain why Durant is proficient with a grenade launcher when he's firing it from a helicopter.
Unable to secure the rights to both The Shadow and Batman, Sam Raimi wrote his own character, capable of changing his own face. Drawing inspiration from The Hunchback of Notre Dame, The Phantom of the Opera and The Elephant Man.
Liam Neeson and Frances McDormand worked closely in rehearsals. They even rewrote the three love scenes they had together after he becomes Darkman. They got through the scenes, according to McDormand, by depending on each other's knowledge of theatre, and each other.
Early preview screenings did not go well as people laughed in the wrong places and complained about a lack of a happy ending. Universal told Sam Raimi that some people rated it the worst film they had ever seen. According to executives, the film was one of the worst-scoring pictures in Universal's history. Then, two preview screenings, one with Danny Elfman's score, went well. Tapert remembers, "the experience on Darkman was very difficult for Sam and me; it isn't the picture we thought it should be, based on the footage we shot and all that. The studio got nervous about some kind of wild things in it, and made us take them out, which was unfortunate." However, Raimi did like the "brilliant" marketing campaign that the studio came up with, releasing posters in advance with a silhouette of the main character and the question, "Who is Darkman?" According to the director, "the marketing made the film a money-maker."
Look-wise, Sam Raimi was interested in paying homage to Universal horror films of the 1930s. Production designer Randy Ser remarked, "if you look at Darkman's lab that he moves into, which is an old warehouse, what was on my mind was Dr. Frankenstein. There were a number of references visually to what we were thinking about in regards to those films."
Sam Raimi hired Chuck Pfarrer as a writer based on his work on Navy Seals (1990). He wrote the first draft and then Raimi's brother, Ivan Raimi (a doctor), wrote drafts two through four with Sam. Ivan made sure that the medical aspects and scientific elements were authentic as possible given the nature of the story. As Raimi and his producing partner Rob Tapert progressed through various drafts, they realized that there was a potential franchise on their hands. Universal brought in screenwriting brothers Daniel Goldin and Joshua Goldin to work on the script. According to Daniel, they were presented with various drafts and "lots of little story documents. There was just material everywhere; drafts seemed to go in many directions." Goldin said that they "spent a lot of time talking and pulling together a way of making the story work. I think that mostly we talked in terms of the nuts and bolts of the story." The Goldins added new lines of dialogue, new characters and bits of action. The studio still wasn't satisfied so the Raimi brothers wrote drafts six through twelve before they had a shooting script.
Among Durant's henchmen, the only one who survives is the one with a machine gun hidden inside a wooden leg. His fate remains unknown, though there is a deleted scene where Darkman kills him with his own prosthetic leg.
Around the time of the film's release, Universal Studios donated $5,000 to Strack Middle School in Klein, Texas, as part of their unique promotional strategy (the school shares the name with Darkman's main villain).