It has been a spectacular turnaround. Harrelson has spent most of his short career, a good 10 years of it, behind the bar of Cheers as Woody Boyd, the affable turnip-headed barman who wouldn't hurt a fly. He was Michael J Fox's (unsuccessful) romantic rival in Doc Hollywood and the goofy honky in oversized shorts who hustled basketball games with Wesley Snipes in White Men Can't Jump.
He became a noted himbo, thanks to a Beatty-like reputation for womanising and a notorious 60ft billboard on which he modelled skintight Calvin Klein underpants and their impressive contents. "It was up on Broadway for, like, two days," Harrelson recalls. "But, man, I've heard no end of it. And I looked kind of better than I was expecting." New York sat up; everybody, wrote one gossip columnist, "was trying to figure what kind of catnip Woody rubs on himself".
It was two signature movies of the early 1990s that made him a major player: Indecent Proposal, in which he sold his wife to Robert Redford for $1m, and Natural Born Killers. And, he is saying now, with a rueful grin, "my agent told me I was second in line for Forrest Gump".
In person, Woodrow T Harrelson is, like most movie actors, a little smaller than expected. He's thinning on top, but the eyes are good and the profile strong: Greek-coin classical. Whether it's the lazy-daisy Texan accent or his surprising ingenuousness, he comes across as a thoroughly regular guy and, yes, a charmer. When he says, "I like being associated with Woody Boyd. Definitely the kind of guy I'd enjoy hanging out with," you easily believe him.
He is scarcely an obvious contender for the role of NBK's Mickey Knox, a psychopathic serial killer; by some accounts Michael Madsen, the ear- lopping reservoir dog, was originally lined up, until Harrelson was brought in at Warner Brothers' insistence. "It was an odd choice, definitely. I asked Oliver `Why me?' and he went [whispering, intense], `I see violence in you.' And at times in my life, if I'd have had a gun, if I'd have had a blunt instrument, I would have been a murderer."
It's undeniable that Harrelson used to like a good scrap (although he readily and disarmingly confesses in interviews to losing most of his fights) and is fond of saying that NBK brought out his "shadow side".
When he was seven, his father was convicted as a hired assassin; he is currently doing life for shooting a federal judge, although he, and his son, profess his innocence. Stone has highlighted this angle - in the film Harrelson as Mickey says, "I came from violence. My dad had it; it's in my blood" - indeed, the director could be suspected of exploiting it slightly. But Harrelson has been reluctant to discuss it.
"Does it bother me? No, it's much too anticipated. But it doesn't have a lot to do with the role I played. I don't perceive my father that way; I don't perceive him as a killer." When he tells me to get lost, it's in the nicest, politest possible way. "To some degree, I don't mind talking about him, but what has bothered me in the past is that the whole article has become that. So I'd prefer to move into something else if you don't mind. Cool."
It's equally probable that Harrelson's background in comedy commended him to Stone, a director not noted for his light touch but trying with NBK for a satire on the excesses of the American media. "I think it started out a little more serious," Harrelson says. "But when we started rehearsals I remember we were always laughing. I can see myself playing stuff for comedy and it really pisses me off at times. There were certain things I would definitely chastise myself for."
And then there is that likeability factor. "I watched a lot of videotapes of serial killers: Bundy, Gacy, the Iceman and Manson, whom I found particularly fascinating - I read his autobiography as well. You can play a character like him and make him extremely hateable, easy. What scares me most is that if you watch Ted Bundy talk, you find yourself compelled. He's intelligent, good-looking, he's making a point. He was one of the most vilified of the killers, I think for that reason."
At that time, back last autumn, NBK was to arrive in the UK just after its Paris opening. Then the film became linked to a wave of copycat murders and a jumpy BBFC withheld a censor's rating (see `What the Papers Said', right). Mickey Knox and his accomplice Mallory (played in the film by Juliette Lewis) stood accused of becoming sexy folk heroes, in life as in the movie. Could it be that Mr Simpatico had done his job too well?
Harrelson gives short shrift to the anti-violence lobby. "The American government is up in arms about the violence in movies, and at the same time it's exporting weapons of mass destruction to Third World dictators. We have a stand-off with Korea, and what do we do at the end of it? We say, `OK, we'll come and advise you on how to build the best nuclear reactors, and we'll loan you the money, to be repaid, of course, at high interest." The whole system kind of boggles my mind.
"What I think NBK is, is a wake-up call. It's making a point about the American landscape, which is in many ways comparable to the English landscape. You don't have the same volume of reality TV, but you do have a lot of tabloid press. In America we're heavily influenced by that Murdoch-style mentality (Murdoch own your paper? Thank God!). It's boring to them to write about the corporations that are polluting your rivers and your air."
Harrelson is a heavy-duty New-Ager. He has stayed in a tent in Africa to work upon his karma, and in an ashram in the Himalayas. In Peru, he participated in something known as a "sweat", which involved sitting in a hut with an Indian and a pile of hot rocks, to which he had to say "Hello, stone people" as they were brought in.
His great passion is the environment. He invented a water-powered watch and a circular beach towel (whose energy-saving properties remain mysterious). Right now he's into hemp, and not (just?) for its narcotic attractions. "You can recycle it and you can grow four or five times as much paper product in an acre as trees, considerably faster. Apparently there's like a hundred alternatives to wood-based paper. I'm funding ways to make them - this is a couple of years down the line, but the research is going on right now. Ultimately, everything I make from that I'm gonna put back into ecological concerns, 'cos I don't need any money; I'm OK."
He used to give interviews on the front lawn of his Malibu villa, in an Indian teepee stocked with drums and crystals. "I've since moved down to Costa Rica, so the teepee's gone. But I'll get one up there, I guarantee. People'll drive by, same way they used to, and say, `There's that crazy Hollywood guy.' " Woody Harrelson: himbo, nice guy, idealist, one of a disappearing breed. We should all drink a toast to him.
n `NBK' opens next FridayReuse content