Holland Taylor sent costume designers Lou Eyrich and Sarah Evelyn photographs of her mother from the '30s and '40s to help with research. They ended up replicating some of the items she wore for Taylor's character, Miss Kincaid.
Samara Weaving, who plays Claire Wood, received an audition for a secret, untitled project and was given a scene to read from the 1959 film Some Like it Hot. She went "full Marilyn Monroe" for the reading, and found out two months later that she had booked a Ryan Murphy show.
Henry Willson, the predatory agent portrayed in this series by Jim Parsons, was a real agent and Hollywood power broker from the late 1930s into the 1960s. Though he did have a handful of female clients, he was most known for representing young, good-looking men who he personally re-christened with ultra-masculine stage names: Roy Scherer Fitzgerald became Rock Hudson; Arthur Gelien became Tab Hunter; Orison Whipple Hungerford became Ty Hardin; Francis Timothy McCown became Rory Calhoun, and so on. Willson was a closeted gay man; although not all of his clients were likewise gay, he became known in Hollywood for having a particular ability to mold young gay men into straight-appearing Hollywood actors. He kept banks of blackmail material on many figures in Hollywood and sometimes deployed it to his advantage or to help his clients, even to the detriment of his other clients. For example, in 1955, when Confidential Magazine threatened to reveal that Rock Hudson was gay, Willson managed to have the story suppressed by trading scandalous information about two lesser-known stars on his roster, Hunter and Calhoun. Willson also arranged for Hudson to enter into a "lavender marriage" with Willson's receptionist, Phyllis Gates, to further quash rumors about Hudson's homosexuality. Hudson retained Willson's representation until the mid-1960s, long past the point when Willson had ceased being a powerful presence in Hollywood; when Hudson fired him, Willson, a chronic alcoholic, threatened to retaliate by throwing acid in Hudson's face. Still, Hudson occasionally gave the increasingly destitute Willson financial support over the years, eventually gifting him $20,000 (worth over $130,000 in 2020). Willson died in 1974 of liver cirrhosis.
Paramount Pictures' original studio lot doubles as the fictional 'Ace Studios', including the iconic Bronson Gate built in 1926, where many scenes from Boulevard du Crépuscule (1950) were also shot, and Production Park, where the surrounding buildings used to lodge the Star's dressing rooms, the Production and the Director's Buildings.
Henry Willson tells the story of William Haines. Haines was in films from 1922-1934, well into the talkie era. Indeed, Haines ranked as a major box-office star at MGM from 1926-1932. As Willson mentions while telling Haines's story to Roy/Rock, Haines was arrested in 1933 for having sex with another man, and when Louis B. Mayer ordered him to enter into a sham marriage with a woman, Haines instead quit MGM and films altogether in 1934. He became a major interior designer to the stars and lived with his longtime romantic partner, Jimmie Shields, from 1926 until Haines's death in 1973. There is a reference to Haines in the classic 1952 movie musical Singin' in the Rain, which is about silent movie stars making the transition to talkies; after the main characters attend an unsuccessful sneak preview of their film The Dueling Cavalier, there is a poster in the theater lobby advertising the silent film Lovey Mary that prominently features William Haines's name.