In accordance with production company guidelines, "Gangster Squad" kept things green on set. "Warner Bros. has a very rigorous eco policy and there's an eco officer on the set," says producer Kevin McCormick. "The plates and forks and stuff are biodegradable, we used biodiesel instead of regular diesel in the generators. We didn't use plastic bottles; we had aluminum water bottles and big jugs of water. We tried to limit the consumption of plastics."

Director Ruben Fleischer did his part by occasionally riding his bike to work "from the production office to set, and I walked to set a few times cause we were shooting in Hollywood a lot. I tried to save on gas."

The film, which opens Jan. 11, is set in Los Angeles in 1949, when mobster Mickey Cohen (Sean Penn) is at the height of his criminal reign and Sgt. John O'Mara (Josh Brolin) has made it his mission to take him down, aided by his titular squad (Ryan Gosling, Anthony Mackie, Michael Pena, Robert Patrick).

"We wanted to bring the glamour of Los Angeles at that time to life," says Fleischer. "It was a combination of the clothes, the cars, the music, the production design that all worked together, and an Academy Award winning cinematographer [Dion Beebe] to capture it all. He lit it so nicely and made it so elegant." The period costumes, "itchy and tight," according to Brolin, helped the actors get into character. "The wool was quite itchy," concurs Gosling. "I had a rash and I channeled that irritation into my hatred for the gangsters."

The characters are based on real people, with some dramatic license taken. Gosling's Sgt. Wooters is "a much braver, more admirable character than the version of him I play in the film. But for dramatic purposes it was necessary to have a conflict, to be affected personally by the death of the shoeshine kid and be provoked into joining the squad," he explains. "I got a chance to meet some family members, his kids came to the set and told me a lot of great stories."

Brolin liked portraying an honorable cop who played by his own rules to get the job done. "I like the fact that he doesn't follow the manual of what the law was back then. I think the boundaries of law were a lot more malleable than they are now. He has to think dirty to snuff out these guys who were trying to turn Los Angeles into a cesspool. He has a lot of integrity."

A climactic fight scene with Sean Penn was the most difficult for him. "We rehearsed for many weeks, and I love the way it turned out," says Brolin. "It's entirely them — no stunt doubles," adds Fleischer. "We shot over the course of three nights starting at midnight to 6 a.m., and it was an incredibly brutal, wet fight." He admits that he was nervous about working with Penn, "but I couldn't have asked for a more collaborative or generous partner. When he jumps in, he jumps in with both feet. He brought so many ideas to the character and the film."

Emma Stone's character, fictional arm candy Grace Faraday to Penn's mobster, was added to the plot to provide a love interest for Gosling. "She wasn't based on a real person, which was a nice jumping off point pressure-wise," says Stone. "She had come to Los Angeles to be famous and she ended up famous by association or proxy. Something pretty heartbreaking is going on underneath the surface."

"Gangster Squad" reunites her with Gosling, with whom she starred in the comedy "Crazy, Stupid, Love." "She owes me money and the only way I can get it back is by doing movies with her," quips Gosling. "We thought it would be fun to work together again, and then we had to try and be serious, I had to pretend I was Humphrey Bogart or something, and that made it difficult," he admits. Stone is up for future pairings, telling Gosling, "I want to work with you a lot, if you'll have me."

Fleischer is encouraged by the response to the film at preview screenings. "I'm proud of how much audiences seem to like the movie," he says. "It has something for everybody, whether it be action, romance, suspense, laughs. It's a real crowd pleaser."

Check out our celeb section and watch Ecollywood videos.

Greening 'Gangster Squad'
Cast and filmmakers discuss the crime-fighting flick.