The amiable Bob Hoskins is always game for a laugh. But a mishap while making new movie Super Mario Brothers quickly wiped the smile off even his face. For the true-Brit actor, star of Hook and Who Framed Roger Rabbit, came within millimetres of being crippled for life when a stunt went terribly wrong.

In the movie, based on the smash-hit video game, Bob and relative screen newcomer John Leguizamo play superhero plumbers hurled into a parallel dimension where lizard-men live. And one scene called for the two of them to be poked with cattleprods by the lizardy henchmen of boss baddie King Coopa, played by Hollywood hellion Dennis Hopper.

But a wayward effects man forgot to put a protective cap on one of the prods. And the pin-sharp point penetrated an inch into Bob’s back, barely missing his spine. The absent-minded effects man swiftly got the boot, Bob says. But the scene itself didn’t. It stayed in the film, which opens in the UK on July 9.

"It looks like great acting," Bob grins. "But it wasn’t. The reaction was real. It hurt like hell. And I knew I’d had a narrow escape when I saw the blood on the end of the prod."

Bob laughs about it now. But, at the time, it was no laughing matter. And it was just one of a series of mishaps which beset Britain’s busiest actor during the making of the $48m movie.

"I was stabbed four times," he tells me. "Twice in the arse. I was electrocuted. I was nearly drowned. And I was almost swept off a cliff-face when 70 gallons of water suddenly poured down on me. Oh, and I broke a finger when someone slammed a van door on it. That scene’s in the movie, too.

"But there are certain stunts that you’ve just got to do yourself because you’ve got to act during them, too," Bob explains. "You accept a certain level of risk."

Does Linda, Bob’s wife, share this action-man outlook? "She doesn’t know about it," grins Bob.

But movie-making isn’t only a physically dangerous business. It can sometimes be mentally taxing too – as Bob discovered, to his cost, when he made Roger Rabbit.

In fact, making the movie came close to costing him his sanity, he claims.

The trouble started, he tells me, when he saw his daughter Rose – now 10, then about five – playing with her imaginary friend, Geoffrey. Noting in particular her apparent ability to physically focus on her friend, Bob asked her to teach him the technique. He reckoned it would add conviction to his acting in Roger Rabbit, where his co-stars were car-Toons that would only become visible in post-production.

But Rosa taught Bob a touch too well. Courtesy of the like-a-child technique, Bob not only tapped into his own imagination, he also externalized it - in the form of self-induced hallucinations. Trouble was, having turned it on, he suddenly found he couldn't turn it off. He couldn't stop seeing things.

"I just lost the distinction between the real world I was living in, and the Yoon world I was working in. And I'd take these hallucinations home with me.

"I remember once," Bob reveals, "talking to my Aunt Vi, who's 80, God bless her - and who'd just lost her friend. And suddenly I saw this Toon-type weasel sticking a big purple dick in her ear. Another time, I was in a bank cashing a cheque - and, all of a sudden, these cartoon weasels were robbing it. They came out of the walls.

"The hallucinations were almost always rude," Bob recalls. "And they almost invariably derived from things they couldn't put in the movie. I used to see Rosa's Geoffrey, too. I've no idea whether I saw the same Geoffrey she saw. But I certainly saw him in the same place she did."

Bob steadfastly maintains that the manifestations weren't symptoms of a nervous breakdown. However, he admits that they materialized during a pretty stressed-out year for him - when a work overload meant constant whizzing between three different countries. Linda hastily took him on a getaway holiday to Antigua - where the weasels suddenly went pop.

"We were on the beach all day," he tells me. "They had no walls to bounce off. Cartoon characters always have to have walls to bounce off."

Now, Bob has a bit of a rep as a tall-tale teller. And, who knows, maybe he's sitting somewhere right now, reading this, and roaring his head off at how I swallowed this hook, line and sinker.

Bob was a plumber himself once, he reveals. "It was in my teens, and I lasted about a week," he recalls.

"My mate was working up a ladder, and I was at the bottom, holding both the ladder and a blow-lamp. Suddenly, this gorgeous bird walked by. And I forgot about the blow-lamp. I set fire to my mate's boot. It was the end of my days as a plumber. I felt so embarrassed, I just had to leave. Mind you, I can't really say that I had much interest in pipes anyway. It never really struck me as a subject I was going to dedicate my life to."

Super Mario Brothers never struck Bob either - not when he was first approached to make it.

"I reckoned I'd made enough kids' films recently," he explains. "And, besides, I didn't know one end of a video game from another. I still don't. I can't figure out which knobs to press. I’m ‘game over’ as soon as the game starts.

"And matters weren't helped much by the reaction I got from my eight-year- old son Jack, when I told him I'd been approached about playing Mario. He said I had to be joking - and that they should get a proper fellow to do it. Mind you, he changed his mind later, when he saw the plastic Mario doll they're selling as part of the spin-off stuff. It looks like me, you see. It's a strange feeling, being immortalized in merchandising. I'm taking the place of the teddy bear."

So why did Bob eventually decide to be game for a laugh, and make Super Mario Brothers?

"[Director] Roland Joffe is an old mate of mine - and he can be very persuasive," Bob explains. "When he makes his mind up about something, there's no way you can turn him down. And he was apparently determined to have me as Mario. I'm the right shape, I suppose," adds the chunky, vertically-challenged actor, with a broad grin.

"But the real killer," he continues, "the thing that really made me decide to do it, was when I heard that Dennis Hopper had been cast as the baddie. He's a real hero of mine - as he should be of anyone who grew up in the Sixties." Had the easy-riding Hopper lived up to expectations?

"Oh, definitely," Bob says. "Do you know what he did, the minute we arrived in Wilmington, North Carolina, to make the movie? He saw this big, beautiful, derelict building that had once housed two theatres, two cinemas and a school. And he bought it. 'I'm going to restore it,' he said. 'Turn it into a film school.' And there's me going, 'But Dennis, it's going to cost a f***ing fortune.' But he's doing it. Even before we finished filming, he'd arranged for [director Francis Ford] Coppola to come and give the opening lecture there."

Bob is full of praise for his Super Mario Brothers co-star John Leguizamo.

"It's tricky turning games sprites into three-dimensional characters," he says, with a certain understatement. "Especially in action movies, there's a tendency to react, rather than act. But John and I put a lot of work building up backgrounds for Mario and Luigi. And he was brilliant. He's only 27 - but he has the comic timing of a 90-year-old vaudeville entertainer."

Their interplay, both on and off screen, helped them through the fairly tough times of a movie whose script underwent constant and ongoing change. "Nobody could make up their mind about it," says Bob. "But the movie eventually sort of made itself. It just took off. Overall, it was quite a lark, what with all the running around shooting at things, all the explosions going off, and all the stunt driving that I got to do."

The most movie fun he's ever had?

"No," says Bob, casually dressed in blue sweater, white slacks and lived-in-looking moccasins, and relaxing in an interview room at a top London hotel, "the most fun I ever had was making Sweet Liberty. There was Alan Alda, Mike Caine and Michelle Pfeiffer also in it. And they put us all in these great big houses in the swanky Hamptons while we were doing it. It was the greatest summer I've ever had."

"I enjoyed Mermaids, too," Bob adds. "But I'll tell you something - there was a sex scene that should have been in there. But we couldn't shoot it, because Cher and I wouldn't stop laughing. I fell out of bed three times."

In the bag, but not yet seen, there's his performance as a dyed-in-the-wool dastard for a Beeb version of Moliere's The Changeling, set to screen in October - and the two weeks' work he contributed to The Big Freeze, pal Eric Sykes's Finland-made follow-up to smash-hit silent film The Plank. For that, Bob, who's 50, risked limb if not life to fall through broken 'ice' into a water-filled rain barrel.

"If a stuntman had done it, it would have been a stunt," says Bob philosophically. "As I did it, it's a sight gag."

Bob's to play Toad in a live-action version of The Wind in the Willows. He's to take the title role in a version of Raymond Briggs's The Man. And he'll maybe take a part in upcoming John Hughes movie Baby's Day Out.

And then there's The Three Bears, the much-mooted contemporary fairytale that Bob wants to make with bosom buddies Phil Collins and Danny De Vito. Yakked about for years, the film now at least has a definite director attached to it. De Vito had intended to direct it himself, Bob reveals - but has now thought better of it. And new man at the helm is apparently Roger Zemeckis, man behind Roger Rabbit and the Back to the Future films.

And what about Bob himself having another go at directing?

"It was like being pecked to death by a thousand pigeons," he says of his first stab - ambitious Anglo/Czech movie The Raggedy Rawney, which disappeared into a distribution black hole when the company backing it got into trouble.

"But I've a couple of things in mind."