For Lin and McCormack, the initial development stages were all about securing a precise tone and approach with their director, and they both agree that the minute they met Fleischer, they knew they had found their man. “When Kevin and I started looking at directors for this we had a really specific mission for this, which is, we're telling a period story set in 1940s Los Angeles, and we wanted to make it feel contemporary," Lin said. "And Ruben's very much a contemporary filmmaker, but he had a real love for history. We knew him personally before the movie started, so we knew he was a history major, he really loves Los Angeles, and we wanted to make this our love song to [the city].”
McCormick returned to Fleischer's statement for the project as “not your father's gangster film,” and said that he wanted “each of the chunks in the movie to be distinguished by its own action language.” Fleischer agreed, saying it was a great opportunity “coming from a comedy background and making the transition to an action-drama movie,” and with Sean Penn filling the larger-than-life shoes of Mickey Cohen, alongside supporting turns from Anthony Mackie, Michael Pena and Robert Patrick, he also wanted to certify a homegrown feel. “It was honestly really important to me that we -- well, Ryan's Canadian -- but we have North American actors not doing accents, and Josh is a seventh-generation Californian. Sean Penn is also a native Angeleno, his grandparents own a bakery in Boyle Heights where Cohen was from, and he used to do bread runs for their bakery in the summers, so there is a very serious, personal connection for many of the actors in the film.”
For the meticulously designed, immersive environments that Fleischer required, he brought on his longtime production designer Maher Ahmad, with whom he shared “a real love and appreciation for history, especially 20th century American history and specifically art deco.” Coupled with the costume design of Mary Zophres, who brought the glamor to Stone's gowns and the leading men's stylish suits, Ahmad's work instantly transports the audience into an exuberant version of '40s LA, one looking to carve its own gangster territory apart from “The Godfather” or “The Untouchables.” However, Brolin believes the film's characters, including his squad leader John 'O Mara, offer a more removed view of justice than what exists today.
“I think [O'Mara] has a lot of integrity, and it's this old idea of someone who has the honor of not following the manual of what law is,” he said. “He had to think dirty in order to snuff out these guys who were trying to turn Los Angeles into the Wild West, into a cesspool.” During Cohen's time, this meant prostitution rings and drug smuggling happening in near-daylight, with the most influential cops bought out from altering that existence. “My dad came to visit us when we were doing a scene at O'Mara's house, and I'd asked him a bunch of stories about what it was like back then. He didn't tell me anything,” Brolin remembered. “But we were looking out onto the street that had been recreated, and he just kind of went off on these stories about how when he was 9 how he used to go in the back and peek in the backdoor of [upscale restaurant] Slapsy Maxie's looking for Mickey Cohen and his goons. He was talking about all this kind of corruption and the idea of gangster as celebrity, yet there was an innocence to everything he was saying and I think that's the difference. The innocence of who O'Mara is, and the idea that you can manifest something honorable and have an impact.”