For the role, Brendan Fraser had to don a heavy prosthetic suit that he wore for hours. According to a piece in "Variety", he told members of the media in attendance at the Venice International Film Festival, "I developed muscles I did not know I had. I even felt a sense of vertigo at the end of the day when all the appliances were removed. It was like stepping off the dock onto a boat in Venice, that undulating. It gave me appreciation for those whose bodies are similar. You need to be an incredibly strong person, mentally and physically, to inhabit that physical being."
At the 2022 Venice Film Festival, Darren Aronofsky said that it took him ten years to make this film. He said casting of the main role of Charlie was the biggest challenge, since he is always looking for actors who are in the right period of their career to play the part. Things didn't get moving until he saw a trailer for the Brazilian film Journey to the End of the Night (2006), starring Brendan Fraser. Aronofsky imagined Fraser as the lead, a hugely popular movie star who had been out of the public eye for years due to a number of personal setbacks, including a divorce.
Following its debut screening at the Venice Film Festival, both the movie and lead actor, Brendan Fraser, were given a six-minute standing ovation. The moment, caught on camera, brought Fraser to tears.
Charlie is loosely based on author Samuel D. Hunter, who wrote both the eponymous play and this movie adaptation. Like Charlie, Hunter is openly gay, taught expository writing at Rutgers University and battled binge eating disorder. Hunter noted that before he lost almost 130 pounds, check-out girls would barely make an effort to act kindly to him, and people would yell abuse at him on the street. Despite early reservations about revisiting this dark episode in his life, Hunter eventually decided to use his isolating experiences with obesity in his play.