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.
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.
James Franco played James Dean in a 2001 television movie biopic. Dean was a huge influence on Tommy Wiseau, and the infamous "You're tearing me apart!" moment in The Room (2003) was inspired by Rebel Without a Cause (1955). James Franco plays Tommy Wiseau in this film.