In the age of social media, casting directors still have managed to find industry newcomers with relative digital obscurity and turn them into bona fide stars overnight.

“It’s exciting to see new actors that you haven’t necessarily seen before,” says Lucy Bevan, who teamed with Emily Brockmann to cast A Knight of the Seven Kingdoms. “As an audience member, you feel like you are discovering them for yourself.”

There are few shows that have been as successful in introducing new faces as HBO’s medical marvel The Pitt. In what they described as “the great experiment,” because of the show’s unprecedented single-shift format, casting directors Cathy Sandrich Gelfond and Erica Berger — who won an Emmy for their work on season one — were given carte blanche to cast more than 250 roles in the fictional Pittsburgh ER.

“Everybody across the board said, ‘Just find the best possible actors for these parts,’ and that’s a casting director’s dream come true,” Berger says. Given the show’s immersive, 360-degree shooting style, the casting directors prioritized theater performers who could move seamlessly between the background and foreground of a scene. Adds Sandrich Gelfond: “We needed people who were fast on their feet because of the intensity. We don’t have marks, so there’s a lot of movement all the time; you have to be very nimble.”

Even with a proof of concept, Sandrich Gelfond admits that casting the second shift, which also featured more than 250 parts, was no less intense. For any given role, Berger estimates that their team receives between 2,000 and 5,000 submitted headshots and résumés. They ask at least 40 actors to submit self-tapes for a guest-starring role — and significantly more for recurring and series regular parts — and then they send five to seven tapes for producers to review for further callbacks, either via Zoom or in person in executive producer John Wells’ office.

Courtney Bright and Nicole Daniels went through a similarly exhaustive process to find the linchpin in Ryan Murphy’s latest FX anthology, Love Story: John F. Kennedy Jr. & Carolyn Bessette. For months, the casting directors pored over hundreds of tapes and scoured social media and talent agencies to find their version of the Kennedy scion. “He had to be a man that every woman would fall in love with and every guy would want to be friends with,” Daniels recalls of the character breakdown.

“We were looking for someone not overly worked-out, not overly manscaped — just somebody who was naturally masculine with hair on their chest and a physique of natural muscles,” Bright adds. That kind of natural masculinity, as it turns out, is hard to find nowadays. It wasn’t until three weeks before the start of filming in New York City that producers selected Paul Anthony Kelly — a Canadian model with little to no professional acting experience — to play JFK Jr.

Chest hair aside, what sealed the deal was Kelly’s “clear” connection with Sarah Pidgeon, who already had landed the role of Carolyn, which extended off the screen after their swoonworthy chemistry read. “Paul had a car, but Sarah didn’t have a car, and we heard that he was going to give her a ride home rather than her taking an Uber,” Daniels recalls. “Courtney and I were both like, ‘Oh, OK, we got him.’ ”

That Kelly was completely unknown to audiences likely has allowed viewers to fully buy into the allure of this retelling of the Kennedy-Bessette love story, Bright notes. “When you come in and have no expectations of what you’re going to see, as an audience member you just get to dive deeper into it than you normally would, [especially] when you get an actor who is portraying somebody so famous with so much history.”

Chemistry between co-leads certainly was top of mind for Bevan and Brockmann, who, in casting HBO’s second GoT prequel, were encouraged to cast a wide net to find newcomers to star as Ser Duncan “Dunk” the Tall and his squire, Prince Aegon “Egg” Targaryen. Per George R.R. Martin’s novellas, “Dunk had to be just shy of 7 feet and Egg is a child,” Bevan notes. But besides the physical parameters, Peter Claffey and Dexter Ansell were able to capture the irreverent, comedic tone of showrunner Ira Parker’s scripts.

Not unlike their characters’ personalities — Claffey captured Dunk’s charming and guileless nature while being “consistently always out of his depth,” and Ansell innately has “a natural superiority and a princely nature,” Brockmann says — the actors quickly took to each other. “We tried to encourage them to spend a little bit of time just chatting before they came in [to read together],” Brockmann adds. “Peter said, ‘Dexter seemed like such a pro. He was really composed and together.’ Peter was intimidated by this tiny 9-year-old!”

Long before they read for a part in front of producers and executives, an actor will spend weeks, if not months, working with a casting director to fine-tune their performance. “When you are casting newcomers, you don’t cast the person you meet on the first day. You cast the actor that they become through the help of directing them and guiding them,” Bevan notes.

Finding a crop of lesser-known actors who can improv is a fundamental requirement of Prime Video’s hidden-camera reality sitcom Jury Duty. While this season’s Company Retreat setting allowed casting director Susie Farris to find actors tailored to specific parts, she and her team still reviewed thousands of self-tapes where actors were asked to tell a story in less than two minutes.

The most compelling — yet least recognizable — actors were called back for a staged focus group of 10 to 12 people. Tasked with a couple of prompts, they were observed to see how they would perform under pressure alongside unsuspecting participants who believed the research study was genuine. “The non-actors are not aware there are actors present; the actors are not told who the non-actors are,” says executive producer Nicholas Hatton of the callbacks. Upon being cast, the actors were given only a month to learn their own fake life and the history they share with other characters at the fictional mom-and-pop hot sauce business Rockin’ Grandma’s.

Farris points out that the mandate of finding lower-profile actors doesn’t apply to just younger thespians. In fact, casting directors relish the opportunity to connect veteran Broadway and West End performers to a wider TV audience. While Sandrich Gelfond says her creative team has “a running list of bigger people” who want to be on The Pitt, she believes the show’s “secret sauce” is “that we don’t hire people who have strong associations” with a particular character. “We’ve been very careful, by and large, to not hire people that we know strongly from recent medical shows,” she explains. “We stayed away from that very much the first season, in that we wanted to create a unique hospital environment.”

Still, there have been occasional opportunities to sneak in some bigger names. Mary McCormack, who played a doctor at a refugee clinic opposite Noah Wyle in ER, scrubbed back in for The Pitt as its chief of neurosurgery; Dann Florek as an elderly man who accidentally ran over his wife; Jeff Kober as motorcycle engineer Duke Ekins; and Rusty Schwimmer as hospital clerk Monica Peters. “It’s all these people that people love that they haven’t seen in a while,” Sandrich Gelfond says, “or they’re just happy to see them.”

This story first appeared in a June stand-alone issue of The Hollywood Reporter magazine. To receive the magazine, click here to subscribe.