Robin Williams: But seriously, Mr Williams...

He identifies with a rusty robot, but Robin Williams has lost none of his spark, says Elaine Lipworth

Comedy comes naturally to Robin Williams, but dramas are more challenging, which is why he often prefers to play psychopaths. He enjoys immersing himself in roles that are as far removed as possible from his own personality. Famous for being the cross-dressing nanny in Mrs Doubtfire, he was equally convincing as a creepy, conniving killer in Insomnia. But in his latest film, Robots, now on UK release, Williams returns to his comic roots as the voice of Fender, a rusty robot made of old household parts including a bright red coffee-grinder. His limbs have a tendency to fall off unexpectedly.

Comedy comes naturally to Robin Williams, but dramas are more challenging, which is why he often prefers to play psychopaths. He enjoys immersing himself in roles that are as far removed as possible from his own personality. Famous for being the cross-dressing nanny in Mrs Doubtfire, he was equally convincing as a creepy, conniving killer in Insomnia. But in his latest film, Robots, now on UK release, Williams returns to his comic roots as the voice of Fender, a rusty robot made of old household parts including a bright red coffee-grinder. His limbs have a tendency to fall off unexpectedly.

"Doing this was a blast - you get carte blanche, and I love doing the voices. I could be wild and then come back and be quiet; I could play and create, " he says. "Fender is damaged like me. He isn't in good shape but he's trying to keep it all together just like I am. He's falling apart. When you hit 50, that's what happens. The scary thing is that I'm losing hair on top but all of a sudden it's growing in other places." He glances at his arms to prove the point.

His hair is grey and the familiar expressive face has become softer, almost avuncular. But ageing jokes aside, Williams, 53, wearing a brightly patterned shirt and beige cords, looks fit. That's partly thanks to a rigorous exercise regime - he cycles around his home in hilly San Francisco. "I can go anywhere there and no one cares, they just go, 'Oh, it's you'," he says.

Williams certainly doesn't act his age. He behaves like a hyperactive child, leaping out of the chair with enthusiasm as he tells a joke. "You get older, but in America they're still advertising things to keep you young. The wonders of medical science. 'Can you make something to increase my thought capacity?' 'No'," he responds in a sonorous advertising voice, "'but we can give you a hard-on that will break the sidewalk'."

Conducting an interview with the star isn't straightforward - the rapid-fire banter is often hard to follow - but it's always entertaining, a hilarious one-man show. The jokes are invariably at the expense of the Republicans, and they trip off the tongue. "What happens to Bush when you give him Viagra? He gets taller. Arnold Schwarzenegger, Governor of California," continues Williams, "now he truly represents the American dream. You come to America, you lift some weights, you do some movies, grab some women, and get elected.

"I often hear something funny that stays with me," says Williams, but sometimes they are old jokes and my wife is always there to 'bust me' and point out that I'm repeating myself." Williams favourite comedians are Chris Rock, Eddie Izzard and Billy Connolly, who is a close friend. "I like people who are irreverent and pushing the envelope. I used to stay with Billy and we'd go to the Highland Games and I'd run the hill race." He switches to a broad Scottish accent. "They'd say, 'Robin Williams is here, Mrs Doubtfire, this is a manly race, you know'."

Over the past few years, the actor has played oddballs and misfits in some unsettling films, such as the obsessive photo-lab assistant in One Hour Photo. There has been very little of the trademark humour that catapulted him into the limelight in 1987, in Good Morning, Vietnam. "Yes, I've been going dark and nasty," he whispers in an exaggerated horror-flick voice. "I just got offered parts I've always wanted to do but never got before because the studios used to say, 'You play nice, warm cuddly people'. Then I was offered characters who seemed nice but weren't necessarily cuddly.

"But if I continue to play Prince of Darkness roles, eventually that will lose its surprise, too. The key is to keep yourself satisfied and the audience wondering about you."

There are no surprises in Robots, though it is visually dazzling. Chris Wedge, who directed Ice Age, has conjured up another thrilling computer-generated world, full of robotic characters with human emotions."I do think robots will have feelings in the future," says Williams. "They'll be programmed to have emotional roles in relationships as wives or girlfriends. Then the programs will become redundant and the robots will be seeing psychiatrists and saying, 'My hard drive is insufficient because I have a floppy disk and premature download'."

Like most contemporary family films, Robots is ostensibly standard entertainment - good vs evil, with the obligatory flatulence jokes. But it also tells an allegorical story about a narcissistic and avaricious quest for perfection. "There are the upper-class robots, the privileged few, but, as you see with the British Royal Family," says Williams, off on a tangent again, and adopting a posh English accent, "all that money and no dental plan..."

His character, Fender, is at the other end of the spectrum from the shiny élite "bots". He's a member of the "Rusties", an impassioned group of working-class optimists who need spare parts to stay alive. "The Rusties are almost the equivalent of homeless people," says Williams. "They are marginal beings and life is tough, they're broke - like most of America right now."

Robots is the first animated film that Williams has made since his captivating turn as the genie in Aladdin in 1992. And he steals the show. He says that he took the part because the film struck a chord on a personal level. "I find it so sweet," he says. "Rodney Copperbottom's dad sacrificed his own dreams and had to be a dishwasher and give up being a musician. Yet he buys his son a ticket to Robot City and says, 'You can do this'. I could really relate to the film, because my parents supported my dreams, and encouraged me to go to acting school. My dad told me, 'Do what you want, I'll help you, but just have a back-up profession'. So I went to one welding class."

Williams was an only child. He was born in Chicago and his family moved around America, making it hard to build friendships. "My father did go to college, but then his father died and his mother was broke and he had to give up college and work in a strip mine in Pennsylvania. Then he went into the navy during the war. And his dreams and career were put on hold.

"It was lonely for me growing up, but it helps with your range as a comedian, and it gives you an imagination. There were long periods of my life that I spent alone. I collected Airfix model soldiers, thousands of them. There was no abuse or anything, but sometimes everyone has an isolated, envious feeling. You only have yourself to play with. You learn how to create games for yourself and you read a lot. It wasn't exactly fun, but later on you find some mechanism that helps you survive. There weren't a lot of kids around when I was small. Then, when I was 12 we moved to a neighbourhood in Northern California. There were kids playing outside on bikes, so I made friends."

Williams studied acting at the renowned Juilliard School. After a stint doing stand-up comedy, he landed a starring role as an alien in the popular TV series, Mork and Mindy. He was already impressing Hollywood with his exciting comedy routines, and his big- screen break was in Robert Altman's Popeye in 1980. He got an Oscar nomination for his starring role in Good Morning, Vietnam, another for Dead Poets Society, and a third for The Fisher King. He finally walked away with a best supporting actor Oscar for Good Will Hunting in 1997.

Along with the hits, there have been some box-office disasters such as Patch Adams and Bicentennial Man. He's not impervious to bad reviews, he says, but at this stage of his career he's happy to take risks and please himself. "I want to work with great people; it is about finding new characters and doing something interesting, different and challenging. I can always do some stand-up to pay the bills."

The bills, of course, don't pose a serious problem for Williams and his family, who live in San Francisco. He has two children with his second wife, Marsha Garces Williams, Zelda, 15 and Cody, 13. The actor also has a 22-year-old son, Zachary, from his first marriage. The family have a house in the city and a vineyard in the Napa Valley. "I don't drink but I sell grapes, it's like I'm an enabler," laughs the actor who gave up alcohol over 20 years ago.

"Fatherhood for me has been the most sobering and wonderful thing in my life," Williams adds. "It is like the ultimate development deal because it changes on a daily basis. When you have a 15-year-old daughter, you are forced to analyse everything, because that's what she is doing. When you have a 13- year-old son who is changing musical taste, from hardcore rap one moment to Nirvana the next, you have to be open.

"The hard thing for us as parents is that we have to say 'Don't make life too easy for them'. My wife enforces that very heavily by saying, 'Yes, you have everything, but you have to find those things that you enjoy doing and work hard for them'. We have to be disciplined rather than just say, 'You have got a trust fund, you're OK'.

"But they are amazing. Zelda is acting and she blows me away. We did a film together recently [ House of D, directed by David Duchovny], and she is so good, so pure, so natural. But I tell her what my father told me, 'If you're going to be a performer, have a back-up profession, something secure, like welding'."