Dancing penguins aren't the only problem when you interview Robin Wiliams, Steve Pratt discovers that the famous funnyman of film is even willing to discuss his recent visist to rehab for alcoholism... as long and answers aren't expected to be too serious.

GETTING blood out of a stone is easier than getting a serious answer out of Robin Williams. Every time, an interview with him turns into a one-man show of jokes, funny voices and inspired lunacy. He's supposed to be talking about Happy Feet, the computer animated hit in which the comedian and actor lends his voice to two penguin characters - Lovelace, a guru who guides young hero Mumble through life's little problems, and Ramon, one of a group of lively Latino penguins.

It's not just with the press that Williams plays the fool. Co-star Elijah Wood says he never really turns off while filming. "We would be having lunch and I would meet five different characters," he explains.

It may seem off the wall humour but director George Miller reckons that Williams couldn't have a career like his unless he was highly disciplined. "He trained at Julliard, he was classically trained. He really loves ensembles. He was incredibly easy to direct. When I was happy with stuff, I let them go and we got improvisation from everyone."

Williams himself rarely stops joking long enough to offer a guide to his art. During the course of the interview topics touched upon include politics, Arnold Schwarzenegger, Britney Spears and recycling.

The price he appears to pay for always performing is a dependence on potentially harmful substances. He's the one who mentions he's just out of rehab. The 55-year-old sought treatment for alcoholism shortly after Mel Gibson's high profile arrest in late July, commenting that "if (rehab) was good enough for him, I'll go. I just think it was kind of like, well, he's in, let's go now."

He said he'd been sober for 20 years when he started drinking again.

It certainly hasn't stopped him working harder than most screen actors with six movies out this year. They don't include a sequel to his hit Mrs Doubtfire because the script isn't right. "If it's not better or at least as good as the first, it's not worth doing," he says. "These films weren't meant to be all at once but they all seem to have happened this year. I'm going to take it easy for a while, take some time off and spend it with my family. It's nice to come out of rehab and say, 'I'm back'. It's like detoxing and going to Colombia. I'll hang out in California and ride my bike."

The real Robin Williams remains reluctant to stand up, prefering to hide behind a succession of funny voices. He pretends to translate into Italian when director Miller answers a question, he does an impersonation of Schwarzenegger, then Golum from The Lord Of The Rings and a brilliant Jack Nicholson.

After several serious roles - in One Hour Photo and The Night Listener - he welcomed getting back in comedic roles in Happy Feet. "It was liberating in a great way. I started off doing four characters and he cut two, which is always liberating," he jokes. "It was great to be doing Lovelace, who is sort of Barry White. And George has a great sense of humour - he's done Road Warrior (Mad Max) and Babe."

Instead of recording the voices separately as is often the case in animated movies, Miller assembled many of the cast together in the studio. When Williams was sharing a microphone with half a dozen Latino comics, his Spanish came in handy. "Gratias," he says responding to praise of his knowledge of the language. "When you're working with five Latino comics you have to have some Spanish."

He's also keen to promote the environmental message that Happy Feet puts forward during the tale of tap-dancing penguins. "There are so many things to talk about," he says. "Whether it will affect policy, I don't know. But little things do make a difference. It's weird to live in the US where we have an administration that says it's not happening."

Then he's off again with more political observations about Donald Rumsfeld, Dick Cheyney and starts singing If I Only Had A Brain in a reference to one political leader. He does his own bit for the environment by recycling - which leads to a joke about a bikesexual ("I ride hard, I ride long") and the fact that you pay more for water than gas (petrol) in the States. "People say I'm a treehugger but I do a lot more than hug trees. If you find a nice knotty pine..." he adds.

He gets to play a real US President - Theodore Roosevelt - in the new movie Night At The Museum, in which the exhibits in a natural history museum come alive at night. His performance is restrained compared to most of his other screen comic turns and none the worst for it. "It was interesting to research him. He was a very brave man and a brilliant Republican, which seems like a contradiction," he says.

Back at Happy Feet, he liked the fact that Ramon the penguin is always trying to impress the ladies. "That's one of the reasons I wanted to do this character - because every one of us has a little macho penguin inside, and I wanted to get in touch with my macho penguin."

* Happy Feet (U) opens in cinemas tomorrow (Friday) and Night At The Museum opens on Boxing Day.