Josh Brolin leads a group of 1940's Los Angeles police officers who seek to take down gangster Mickey Cohen (Sean Penn) in the based on a true story Gangster Squad. Movie Fanatic caught up with the star as he dishes finding his Golden Age of Hollywood modeled character, how his father James Brolin influenced his performance and why that fight between him and Penn nearly caused some real injuries.

Movie Fanatic: You play a real life lawman who took down gangster Mickey Cohen. Did you get to talk to the family of John O’Mara?

Josh Brolin: We got to talk to John O’Mara’s daughter. You kind of create a composite character and see how it works.

Movie Fanatic: Did your portrayal of him get altered in any way after those discussions?

Josh Brolin: This was less of a laconic character when we filmed it. Then in editing and all that, we found it much better to have me shut up and go for more of that Bogey, Clint Eastwood type thing. It seemed to balance things out better. So even what you do on the set isn’t necessarily right. Thank God for editing [laughs].

Movie Fanatic: Your O’Mara, like the real guy, is a war hero returning to a home city of L.A. he hardly recognized, as teased in the Gangster Squad trailer. What did you most identify with him?

Josh Brolin: I think he has a lot of integrity. I like the fact that it’s this kind of old idea of somebody who has the honor of not following the manual of what they say law is back then. I think the boundaries of law were a lot more malleable then than they are now. The good guy was not necessarily the good guy. He had to think dirty in order to snuff out these guys who were trying to create Los Angeles into the Wild West... a cesspool. After he got back from World War II, I think he was shocked at how much Los Angeles had changed.

Movie Fanatic: Director Ruben Fleischer truly captures the essence of 1940’s L.A. Did you ask your dad for guidance about that time, given that your family is seventh generation California natives?

Josh Brolin: My dad came to visit us. We were doing the scene at O’Mara’s house one day. I had asked my pop a bunch of stories like what was it like back then. He didn’t tell me anything. But he finally got to the set one day. We were looking out on the street that had been recreated, and he just kind of went off on these stories about when he was nine years old, how he used to go in the back and peek in the back door of Slapsy Maxis looking for Mickey Cohen and his goons and all that kind of stuff.

Movie Fanatic: Did he have a take on how gangsters were seen back then?

Josh Brolin: Yes, he talked about all this kind of corruption and all these kind of gangster stories or the idea of gangsters as celebrities back then. And yet, there was an innocence in everything he was saying. I think that was the difference.

Movie Fanatic: You starred with Sean Penn before (with all those great Milk quotes.) He’s an intense actor, no?

Josh Brolin: I don’t know, man. It’s Sean [laughs]! We’ve known each other for a long time. I don’t find him very intense, myself. But he’s an amazing actor. We have a lot of fun. We work similarly. He’s the same guy who was Harvey Milk, you know what I mean?

Movie Fanatic: His talent runs the spectrum…

Josh Brolin: That’s the shocking thing about Sean! His conviction is so complete when he’s doing something. But then you remember as a fan, you think, "Holy (expletive), this is the same guy who was Jeff Spicoli!" That’s kind of what makes him, at least to me as a fan, so special.

Movie Fanatic: You guys have quite a confrontation scene. Did it ever get too real?

Josh Brolin: I think the fight with Sean was the most difficult because Sean didn’t rehearse as much as I did. So, his fists were flying wildly during the fight hoping that they got something that was useable. It was a tough fight that we rehearsed for many, many weeks. I love the way that it turned out. But I think both of us, being the current and ex-smokers that we are, that was the most challenging on an oxygen level [laughs].

Movie Fanatic: Did any punches connect?

Josh Brolin: [Laughs] Possibly!

Movie Fanatic: The cast is stellar, between you and Penn, Ryan Gosling, Emma Stone, Michael Pena and Anthony Mackie….

Josh Brolin: Well, let’s just say that you start these things out and you have this studio-propelled, value dream team and you’re trying to get -- I won’t mention any names -- but you’re trying to get who’s of most value. It’s kind of great when that doesn’t necessarily work! I think we came out with an amazing cast. A lot of those guys are lead guys now. Why would they do smaller parts like that? Because Gangster Squad is just that good, we all wanted to be a part of it.

Movie Fanatic: What’s up next for you after Gangster Squad?

Josh Brolin: I did Labor Day and then I did Oldboy after that. Oldboy is going to be great. It should not be but I think it’s going to be. I think we got in there and we went, "This could be a stinker." But, something came together. Spike Lee was fantastic. There’s some really good stuff there.