CHADWICK BOSEMAN

The actor was in Zurich promoting his James Brown biopic, Get On Up, when his manager pulled him off a red carpet with an urgent call. It was the Marvel Studios team, including Kevin Feige and Captain America: Civil War directors Anthony Russo and Joe Russo, who said they were including Black Panther in the 2016 film and wanted Boseman to play him. The actor had auditioned for the role of Drax in Guardians of the Galaxy, and while it didn't work out, he impressed the team, who kept him in mind for something else — no audition required. "He was someone we all felt really strongly would be amazing as Black Panther," says Finn.

ROBERT DOWNEY JR.

Marvel took a leap of faith on Downey — who at the time was an Oscar-nominated actor whose career had taken a hit after personal and legal issues. Downey, too, was taking a leap of faith on Marvel, agreeing to screen-test for an upstart studio that had no films to its name. "It was an unexpected choice," Finn says of the Iron Man casting. Downey went on to anchor the Marvel Cinematic Universe and would earn unimaginable paydays for the role ($50 million for 2012's Avengers). A decade after he auditioned for 2008's Iron Man, Downey would record his final lines ("I am Iron Man") on the soundstage next door to where he auditioned.

CHRIS EVANS

"It was a nail-biting time," Finn recalls of wooing Evans into picking up Captain America's shield. The actor had turned down the role multiple times, but after a thorough search, Marvel was convinced Evans was the only person who could play Steve Rogers. "He had a sense of humor, he had depth, he had a beating heart and a nobility," says Finn. "Ironically, his very reluctance to take the part showed how perfect he was to play Captain America."

DANAI GURIRA

Because Marvel is so secretive, scripts aren't given out to actors until after they're cast, so they must trust that the movie is going to be good. That was the case with Danai Gurira, who even by Marvel standards was busy, thanks to a grueling Walking Dead schedule and her work as a playwright. To get her to sign on, Marvel had to pull back the curtain on Black Panther character Okoye, a general who'd go on to have roles in two Avengers films. "It was the process of letting her know what the creative elements were and what she could hopefully do with the part," says Finn. "She crushed it."

CHRIS HEMSWORTH

The first time the future God of Thunder met with Finn, he'd just stepped off a plane and had rushed to Marvel's Burbank headquarters. Over the ensuing months, the actor tested multiple times and was put through the ringer by Thor director Kenneth Branagh, who made him use Shakespeare in his audition. During the casting process, he gained confidence by doing a press tour for his small role in J.J. Abrams' Star Trek. He was on the set of horror film The Cabin in the Woods when he was finally cast, in 2009. "It didn't happen overnight," Finn says of the lengthy process. "But by the end of it, everyone, including Chris, agreed that he was the perfect person to bring Thor to life."

TOM HOLLAND

There was no greater pressure for Finn than finding the next Spider-Man. Not only was the character Marvel's most popular superhero, but two other actors had inhabited the role over the previous decade. Marvel was determined to find someone young enough to believably play a high school student for his debut in Civil War, and saw more than 2,000 actors. Tom Holland auditioned six times, culminating in a chemistry test with Downey. Downey was invested in the casting, as he knew Tony and Peter would have a multi-film arc together. "He not only screen-tested with [Tom], he really spent some time with him to make sure they were comfortable and could do their best," says Finn.

SCARLETT JOHANSSON

While Marvel and Lucy have made Scarlett Johansson an action star, she wasn't known for her butt-kicking back in 2009, when she was cast as Black Widow/Natasha Romanoff in Iron Man 2. A decade later, she's preparing for her first solo movie as the character, and Finn credits the actor's vision for making the character become a fan favorite. "Maybe it would have just been in one or two films," says Finn. "But I think her take on the character was so compelling and thoughtful that it grew to where she's really becoming a selfless leader, which is not where Natasha starts."

LUPITA NYONG'O

Marvel had been eyeing the actress even before 12 Years a Slave won her an Oscar and made her one of the most in-demand actors in Hollywood; she previously had auditioned to play Nebula in Guardians of the Galaxy before joining Black Panther as Nakia. "She was a straight offer," notes Finn. "She had been on our radar for a long, long time, and is an incredible, exceptional talent."

CHRIS PRATT

There were a number of obstacles on Chris Pratt's path to playing Star-Lord in Guardians of the Galaxy. To start, the actor was known as the lovably schlubby Andy Dwyer on NBC's Parks and Recreation — nothing about him screamed ripped action star. Even worse: Filmmaker James Gunn didn't want to meet with him for the role, and when Pratt got wind of the director's hesitance, he in turn didn't want to come in to audition. "That was a challenge," says Finn of Pratt, who previously auditioned to play Captain America. "But when the two of them met, the rest was history. They got along like a house on fire, and I think that relationship really gave rise to Star-Lord."

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