Quiet believability is important in almost any show, but it’s crucial in The Outsider. As a show about people suspending disbelief in the supernatural, it only works if the actors’ reactions are subtle and credible. With the exception of Jason Bateman, who only appears in the first two episodes, it’s a show full of recognizable faces who aren’t necessarily household names—and that was a result of the show’s priorities. “The goal is to tell the story, focus on character, and people the world with great actors who aren't going to take you out of that,” says casting director Alexa Fogel.

It helped that Mendelsohn, who can disappear as well as any actor, was the first name attached to the series. Fogel was then tasked with building a tapestry around his hangdog eyes and weighty certainty. No casting director has a more intimate relationship with prestige TV than Fogel, who has served as casting director for era-defining shows like Atlanta, The Deuce, True Detective, Ozark, Banshee, Generation Kill, and The Wire. And while fans of those shows will spot a few Fogel favorites in The Outsider (Marc Menchaca, who plays the bad-tempered police officer Jack, was in Ozark and Generation Kill; Derek Cecil, who plays Holly’s love interest Andy, was in Banshee), her overriding focus was experienced actors, and especially ones with theater backgrounds.

Marc Menchaca in The Outsider, 2020. Courtesy of HBO

The reason Fogel erred towards actors who were theatrically trained, she says, was because of the versatility the material required. Actors like The Ferryman’s Paddy Considine or Menchaca, for instance, had to be able to play dual roles: a character, and then a version of that character that’s been touched by—or is—El Cuco. “The real challenge [for Considine, for instance,] is how you can play an everyman from Tennessee and someone transformed to something scary, controlling, and carnivorous,” says Fogel. “When you've seen someone do a bunch of plays, you have an understanding that the instrument can do more than one thing.”

For the actors’ part, the lift was made easier by the material, which was adapted from a Stephen King book by the great crime fiction author, Richard Price. “Richard's dialogue flows so easily and so well,” says Menchaca. “His writing style is easy for actors to work with, and it helps in bringing about a natural and understated performance.” Bill Camp, who also appeared in Price’s The Night Of, attributes the ease to the “cadence and rhythm” of Price’s dialogue: “There's a certain kind of music. [Richard]'s tapped into a natural form of expression we have somewhere.”

Bill Camp in The Outsider, 2020. Bob Mahoney / Courtesy of HBO

The naturalness of the dialogue helped Menchaca, Camp, and the rest of the cast sink into their roles seamlessly—but so much so that the show’s performances largely aren’t what fans of the show are talking about. Redditors are more consumed with predictions and theories. And Camp says that when he gets stopped on the street by fans of the show, it’s usually to ask him what happens next. But make no mistake: that’s how he prefers it. “I like the anonymity of that a lot,” says Camp. “If somebody does see me, it's great that they're so into the story because that's really all I am ever—a very tiny part of a much bigger story.”