At an abandoned Pasadena hospital, Woody Harrelson patiently waits for a shot to be set up as he plays with the gold jewelry on his fingers. He’s decked out like a slick street hustler, a scorpion tattoo on his neck. Across the way, Christopher Walken is primped by makeup artists, a faux bloody wound on his head tended to.

“I can’t believe I’m doing a scene with Christopher Walken,” Harrelson says. “I love him. You never really know where you stand with him, you know? You’ll be talking and you won’t know. And then he’ll crack a big smile suddenly.”

“That’s kind of like you,” I tell him. He cracks a big smile suddenly.

The scene is set and Harrelson takes a seat opposite Walken. It’s Walken’s close-up. Harrelson is wrapping up his day off screen, giving Walken something to work with as they perform a hilarious scene regarding a cravat. (The film is Martin McDonagh’s dark comedy “Seven Psychopaths.”) This take, McDonagh wants Harrelson to make Walken laugh. The camera rolls. “It looks like your neck threw up, man,” Harrelson says. Walken laughs.

Later, in Harrelson’s trailer, the actor still can’t shake the moment, obviously a high point.

“I can’t fuckin’ believe I just did a scene with Christopher Walken,” he says, digging into a freshly delivered raw food meal. Harrelson is a known vegan but he says he eats raw whenever he’s shooting to keep the energy up and avoid the mid-day, post-lunch crash.

The conversation lingers on any and every topic but “Rampart,” the film he’s promoting and for which he could receive an Oscar nomination for perhaps his greatest performance to date. We talk about Lars Von Trier and his Cannes gaffe, which Harrelson can relate to. His PR handles him tightly sometimes and he admits it can be frustrating, but he also admits he’s said some things that have gotten him into hot water before.

“To me, that”s one of the most brutal things now in our society, is how unforgiving it is,” he says. “If you say anything, even in that kind of context where you”re trying to joke, you lose your way, the next thing you know you can”t even come to your own movie. It seems to me like you always have to look at where a person”s coming from, you know? But he”s always said outrageous shit. I guess it’s understandable. I mean, Hitler is the one area that people just can’t seem to joke.”

He pauses for a moment and considers.

“Having said that, I wrote a play with a buddy called ‘Bullet for Adolph.’ If it don’t make you laugh, I’ll give you your money back.”

The conversation transitions to theater, where Harrelson likes to stretch from time to time. He opened “Bullet for Adolph” in Toronto in the spring and hopes to take it to New York soon, but he has no plans to take it to Los Angeles because the climate rarely feels right for theater.

“Ironically, you see good plays here because people putting plays on here have got to be serious,” he says. “But I realized trying to do plays here years ago, that it just did not feel like a theater appreciative kind of city. The audience who comes is going to be appreciative, but just generally, trying to get people into the theater, it”s very hard here.”

We talk about “God of Carnage,” which Harrelson loves. (“That woman is one of the true great writers,” he says of playwright Yasmina Reza.) We talk about TV. (“I started watching ‘The Wire,’ dude, I went through that thing in two weeks. And I was shooting a movie at the time.”) We talk about health and diet. (“The state of the health of the individual is equivalent to the state to the health of the colon,” he says, providing the world’s greatest sound byte ever.)

He pitches the raw food way, convincingly, and then we talk about politics. (“I kind of think that anybody who gets into the office of president has to kiss the ring and do as they’re told. And I think the day that war became the most lucrative industry was a sad day for this world.”) The conversation covers mountain top removal and marijuana before eventually coming to the topic at hand: Oren Moverman’s “Rampart.”

The press rounds on this one have been pretty intense, he says. He recalls a meeting he was called into recently expressly for the purposes of reminding him that there will be more interviews coming. And with good reason. “Rampart” is a film that was picked up out of Toronto with a mandate for a 2011 release and an eye toward awards season. And there is an argument for Harrelson, whose performance as a corrupt LAPD officer is staggering, a marvel of internalization on one hand, an explosive revelation on the other.

Yet the role is a unique one for a guy like Harrelson, “a lazy, happy hippie from Maui,” to take. As was his role in Moverman’s last film, “The Messenger,” which placed Harrelson in the role of a military officer.

“I can say, the two particular roles of any occupation, military and police are about the hardest for me to imagine being,” he says. “So, to me, it was a really exciting challenge. With ‘Rampart,’ I read it and I”m like, ‘That”s the best role I”ve ever been offered. Phenomenal.’ But, I was daunted, you know? Like the concept of trying to be a cop. It”s just bizarre, man. Bizarre to even think about.”

Indeed, a few weeks earlier at a post-screening Q&A for the film, Harrelson noted that he felt like he was wearing a Halloween costume when he first looked at himself in the mirror, wearing an LAPD uniform. But he absorbed a lot by going on ride-alongs with real LAPD officers.

“The best thing is hanging out with these guys,” he says. “They really did help me. More than all the books I read or the documentaries, that was the number one thing. Seeing a whole other world. I met a lot of gang-bangers that, I was like, fuck, I could see hanging with these guys. Granted, maybe they do unspeakable things that I”m obviously not seeing them do, but, some fuckin” good guys, you know?”

Harrelson came to Los Angeles maybe two months before production started. He fasted because he wanted to lose weight. He ended up dropping 30 pounds, honing in on the external aspects of the character, ridding himself of his Texas accent. The whole time he was nervous, though. Just as he couldn’t believe himself as a cop, he was worried no one else would be able to, either.

“It took a long time,” he says, “and then, finally, it clicked.”

There’s a lot Harrelson says was cut out of the film, which ultimately stands as an abstract assemblage in some respects (and is all the more powerful for it). “Probably at least three dozen scenes,” he says, “big and small, were cut. And also characters. I give credit to Oren. He was a great director through the shoot and then he became a sculptor in the editing room. And he created something that I think is beautiful.”

The press rounds are taxing. He admits, like all actors and filmmakers, that it’s his least favorite part of the job. But he also understands that it’s hardly something worth complaining about. After all, who wouldn’t want to be in Woody Harrelson’s shoes?

“That is what I discovered the time I took like several years off,” he says. “I was planning on maybe three years and it turned in to five. But even in there I did a play here, I did maybe like a small part in something. The biggest part was I just wanted to spend more time with my kids, but another part was I wasn”t enjoying it. I wasn”t enjoying the whole business. I was just doing movies back-to-back-to-back, press all in between. I mean it was like two full-time jobs. I don”t know any other business where they have these kind of hours. Well, maybe cops do.

“That was 1997. And I think it was a great thing to do. When I was ready to work again, I was enjoying it again. Because I feel like if you”re doing this job and you”re not having fun, I mean, you’ve got to walk away. Getting to be out there, sittin” there with Chris fuckin” Walken, trying to make him laugh. I mean, this is a good job.”

“Rampart” opens in theaters nationwide Friday, January 27.

For year-round entertainment news and awards season commentary follow @kristapley on Twitter.

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