Greg Sestero stated that when he was writing the book, Tommy Wiseau said that only two actors could play him in the adaptation: James Franco or Johnny Depp. Wiseau, who claims to have once lived in New Orleans, was a fan of Franco's performance in the film Sonny (2002).
James Franco spoke like Tommy Wiseau throughout each day's filming, and even directed using Wiseau's distinctive voice and syntax, though Jason Mantzoukas said that Franco did not direct in character and only spoke like Wiseau. Seth Rogen admitted he had a hard time being directed by Franco while being interviewed on The Howard Stern Show. Rogen said during the first two days, he had a hard time containing his laughter as Franco was speaking as Tommy Wiseau with his notable European accent. Franco told Rogen he would get used to it, which he eventually did.
In real life Greg and Tommy did not move to Los Angeles at the same time. Wiseau offered his LA apartment to Greg rent free for several months, while Tommy came and went from San Francisco at random. Once Greg had booked some small gigs Wiseau suddenly moved in full time to the LA apartment, demanded rent from Greg and set up the divider in the living room as seen in this film.
At a Q&A screening of The Room (2003) (before production of this film began), Greg Sestero expressed interest in playing the actor who was originally cast as Mark, who Wiseau fired and replaced with Sestero himself. However, this element of the true story was left out of the final film.
Over 20 minutes of The Room was painstakingly recreated for this film, including almost exact body movements and lines spoken at nearly identical timing to the original. The Disaster Artist ends with side-by-side comparisons of these scenes. However, the way in which some lines were poorly dubbed in the original was not recreated.
Besides an interview for Esquire and a video for Funnyordie.com, brothers James and Dave Franco have never worked together or appeared on-screen together until this film. Dave Franco almost appeared as himself with his brother in This Is the End, but he was later excluded because his charcter would have had to die and it was considered too sad for the already dark comedy.
In almost every interview for The Disaster Artist, James Franco mentions that Tommy Wiseau approves of "99.9%" of the film. His only objections were the lighting of the first scene, which Franco believes was because Tommy was wearing sunglasses when watching the scene, and also for the poor way James threw the football.
James Franco played James Dean in a 2001 television movie biopic. Dean was a huge influence on both Tommy Wiseau and Greg Sestero, and a major bonding point for their early friendship as detailed in the book and shown in this movie. Even the infamous "You're tearing me apart!" moment in The Room (2003) was inspired by Rebel Without a Cause (1955). Years later when James Franco approached Tommy Wiseau to play him Franco learned that he was already a fan of the 2001 James Dean biopic which gave Wiseau the confidence it was the right choice.
To promote the film the distributor rented the same billboard on Highland Avenue in Los Angeles that Tommy Wiseau rented for five years to promote The Room (2003), mimicking the layout of the original billboard and including a phone number to RSVP to screenings.
In actuality, Greg Sestero was never offered a part on Malcolm in the Middle (2000) by Bryan Cranston. Also, Cranston did not begin directing for the series until 2003, a year after The Room (2003) wrapped filming. Sestero stated in his book that he had a beard while filming The Room until Tommy Wiseau spontaneously decided he should shave it off for the tuxedo scene, and was hesitant do so because he felt having a beard was his disguise and "a key component of my Room anonymity strategy".
In his book, Greg Sestero stated after his first rehearsal with Tommy Wiseau they played soccer, not football as shown in the film, though Wiseau still shouted "touchdown" after scoring a goal on Sestero.
Michael Rousselet, who is credit as "Patient Zero" of The Room's cult phenomenon, snuck onto the set for the final scene and is one of the first audience members to high five James as he runs down the aisle.
In The Room, the character of Peter, the glasses wearing psychiatrist friend who falls down while playing football, suddenly disappears and a new character named Steven appears in the movie with no introduction and speaking lines that would logically have made sense with Peter. However, The Disaster Artist film makes no mention of this and seemingly implies that Peter (played here by Nathan Fielder) was present for the entire film.
Greg Sestero is 6'2, but Dave Franco is 5'7. Tommy Wiseau is 5'9, and James Franco is 5'11 which puts him somewhat convincingly in the ballpark to play Wiseau. Greg Sestero is 5" taller than Tommy Wiseau, but James Franco is 4" taller than his brother, Dave. So while the real Sestero was looking down at the real Wiseau while filming The Room, in the film "The Disaster Artist" Franco Wiseau will be looking down at Franco Sestero from roughly the same height difference.
In actuality, Greg Sestero had no interest in acting in The Room (2003) and originally only intended to serve as the film's line producer, and Tommy Wiseau had cast a different actor to play Mark. Wiseau spontaneously decided the night before filming began that he wanted Sestero to play the role, and Sestero reluctantly accepted after Wiseau offered him a substantial pay raise and a new car. Rather than telling the original actor that he had been replaced, Wiseau had him come to set and perform his scenes for weeks, but instructed the camera crew not to roll any film.
The scene between Greg Sestero and Tommy Wiseau during the premiere of The Room (2003) was largely an invention of the film, as Sestero's book makes no mention of how the audience received the film during its premiere, only that Wiseau was brought to tears by how happy he was. Robyn Paris stated in an interview with Entertainment Weekly in 2008 that most of the audience was "crying with laughter". Sestero also said in Q&A screenings that people who attended were disappointed but amused while some walked out with negative comments heard by Wiseau and Sestero.