Development
Artisan Entertainment announced a deal with Marvel Entertainment in May 2000 to co-produce, finance, and distribute several films based on Marvel Comics' characters, including Deadpool. By February 2004, writer and director David S. Goyer and Ryan Reynolds were working on a Deadpool film at New Line Cinema. They had worked together on the Marvel film Blade: Trinity. Reynolds was interested in the part of Deadpool after learning that in the comics the character refers to his appearance as "Ryan Reynolds crossed with a Shar-Pei". New Line Cinema executive Jeff Katz, who thought Reynolds was the only actor suitable for the role, championed the idea. However, there were rights issues with 20th Century Fox and their X-Men films, and the project did not move forward.
By March 2005, Reynolds learned that Fox had expressed interest in a film featuring Deadpool. The character was set to make a cameo appearance in the 2009 film X-Men Origins: Wolverine, with Reynolds cast in the part. His role was expanded during the film's production. Katz was an executive at Fox at that point and said that Deadpool was "nicely set up to be explored in his own way" in a future film. The film's portrayal deviates from the original comic character, "imbuing him with several superpowers and sewing his mouth shut". Deadpool apparently dies in the film, though a post-credits scene showing him still alive was added to the film shortly before its release. After the successful opening weekend of Wolverine, Fox officially began development on Deadpool, with Reynolds attached to star and X-Men producer Lauren Shuler Donner involved. The spinoff was set to ignore the Wolverine version of Deadpool and return to the character's roots with a slapstick tone and a "propensity to break the fourth wall".
Rhett Reese and Paul Wernick were hired to write the script in January 2010. Reynolds, who worked closely with them, said they were chosen because, "Tonally, they got it. They just [understood Deadpool] right off the bat." By that June, Robert Rodriguez had been asked to direct the film. He confirmed this a month later, saying he had been sent a "really good" script and was considering taking on the project. By October he was no longer interested in it, and Adam Berg was being looked at to direct the film. In April 2011, Tim Miller was hired after working on the visual effects for some of the X-Men films, in part because of his work creating animated short films. These included the Academy Award-winning Gopher Broke and a DC Universe Online trailer, which was "epic and cinematic, everything [Fox wanted] their comic book movies to be". Miller would make his directorial debut with the film, while Reynolds closed a deal with Fox to produce the film.
Reynolds took on Green Lantern after Fox had no intention on making the project. The film was released later in 2011 and was a critical and commercial disappointment. This tainted the Deadpool project. Fox executives were already concerned about its R-rated content. After several meetings the studio agreed the film could not be reconfigured for a more traditional PG-13 rating, and gave Miller "a low-six-figure budget" to produce some test footage. He created the footage using CGI at his animation company Blur Studio in 2012, with Reynolds voicing Deadpool. The footage did not convince Fox to green-light the film. After the successful May release of Marvel Studios's The Avengers, Reese and Wernick thought Deadpool might be approved as an already developed superhero film. Fox was actually even more doubtful about the script, however, and began exploring ways to include Deadpool in an Avengers-esque team-up film. At different times during development, James Cameron and David Fincher, both friends of Miller, read the film's script and championed the project to Fox executives.
The test footage was leaked online in July 2014, and was met with an overwhelmingly enthusiastic response. That September, Fox gave Deadpool a release date of February 12, 2016. Production was set to begin in March 2015, with Simon Kinberg joining as producer. Reynolds attributed Fox's green-lighting of the film entirely to the leak. He, Miller, and the writers had previously discussed leaking the footage themselves, and Reynolds initially thought that Miller had done so. He later believed the leak came from someone at Fox. In exchange for being able to make the film the way they wanted, Fox gave the crew a much smaller budget than is typical for superhero films. In September 2025, during the Toronto International Film Festival, Reynolds admitted that he leaked the footage.
Reese and Wernick wrote a draft of the script every year for six years before completing the film, with around 70 percent of the first draft ending up in the final film. Reese described Reynolds as "the keeper of the Deadpool flame for many years ... if we ever do something that is off the Deadpool path, or if it doesn't feel like Deadpool, he catches it." The writers did not want the film to be an origin story, but Reynolds disagreed. They settled on a "modern" Deadpool story as well as the origin story connected by Deadpool's narration and fourth wall breaking. This helped to balance the darker origin story with the cartoon-like Deadpool scenes. It also allowed the opening fight sequence to be extended through the first half of the film (with the origin story told throughout), saving money on additional fight scenes. This fight sequence labeled the "Twelve Bullets Fight" reimagines the original test footage. Once the origin story is told, Deadpool uses a "fast-forward button" to return the audience to the present day.
In October 2014, Kinberg confirmed that Deadpool would be set in the same shared universe as the X-Men films, but would "stand independently". The writers wanted a traditional X-Man in the film as a foil to Deadpool and felt Colossus was a character who had not been explored much in previous films. Miller wanted "more superhero stuff", instead of "just Deadpool and a lot of guns". The character Negasonic Teenage Warhead was added as a trainee X-Men mentored by Colossus. She was chosen for her name from the list of comic characters available for use by Fox. The characters Garrison Kane, Wyre and Sluggo were included in the script at one point, but ultimately removed for budgetary reasons. These villains were replaced by a single character, Angel Dust. Cannonball, Emrys Killebrew, Patch and Tar Baby were also considered. The character Cable was also set to appear, but was eventually pushed to a potential sequel so this film could "get Deadpool on his feet" first.
The writers worked to keep the script's pop-culture references up-to-date throughout its development. Kinberg confirmed the film would make fun of Deadpool's portrayal in X-Men Origins: Wolverine. It also includes jokes at the expense of Green Lantern. While Miller felt it was okay for audience members not to understand all of the film's jokes, he wanted to avoid anything targeted specifically at comic fans. He was not in favor of any joke the audience "needs to look up on the internet" after the movie ends. The film's post-credits scene is a parody of the equivalent scene from Ferris Bueller's Day Off (1986), where the title character of that film breaks the fourth wall like Deadpool. In the parody scene, Deadpool wears a bath robe and tells the audience to go home. He also confirms that Cable will appear in the sequel. After reading the scene, a Fox executive described the film as a combination of Ferris Bueller's Day Off and Natural Born Killers (1994), a description the writers felt was accurate.
Forty-eight hours before the film received the official green light from Fox, the studio cut its budget by $7–$8 million down to $58 million. This forced a last minute re-write that saw about nine pages cut from the 110-page script. Changes included the removal of a motorcycle chase at the end of the Twelve Bullets Fight and having Deadpool forget his bag of guns before the final battle sequence to avoid having to shoot a costly gun fight in the third act. Reese said, "It was that last, lean and mean chop that got us to a place where Fox was willing to make it. The script was very efficient and not too long. That was a function of budget more than anything, but I think it really made the movie pace nicely."
