Meeting Dan Castellaneta was always going to be weird. When the hotel door opens and the man who plays Homer Simpson appears, it’s clearly impossible for him to look like Homer, talk like Homer or be washing down doughnuts with endless cans of beer – but hope springs eternal. Face to face with Castellaneta, however, that hope is softly dashed. It’s like telling a child there’s no Father Christmas, or realising your date won’t be calling back. The real Mr C is a slight, gently spoken man with fine, angular features. Like Clark Kent to Superman, he is mild-mannered, dapper and polite. Indeed, all he shares with his cartoon alter ego is a smattering of male-pattern baldness. When I spill some water, he doesn’t even say “Doh!” He reaches for a napkin and helps me mop it up while we make polite small talk.

“Being Homer can be a blessing and a curse,” he nods when the vast, yellow elephant in the room can no longer be ignored. “We did the movie and they wanted me to go to Australia and do the public appearances. I thought – why? It’s not going to help my career on camera, and it’s not going to help Homer get more movie roles, so all it would do is blow my anonymity. I can walk down the street without being bothered, despite starring on primetime TV all over the world. It’s a double-edged sword, though. Homer is an international movie star, but I don’t get inundated with roles. I have to audition like everybody else.”

Although he also voices Grampa Simpson, Krusty the Clown, Groundskeeper Willie, Mayor Quimby and, as they say in showbiz, many more, it’s Homer who defines Castellaneta. Plenty of his nonSimpsons screen work has been Homer-related. In a cameo in the recent film The Pursuit of Happyness, he asks Will Smith for a doughnut; in the sit-com Arrested Development he’s an incompetent doctor who cries “Doh!” after leaving instruments in a patient. In April, he became the actor with the longest-running character on American television, overtaking the previous 20-year record held by Kelsey Grammer for Frasier.

Doesn’t this make him resentful? Doesn’t he ever want to tear at Homer’s fatuous grin and scream, “Give that fame to me!”? After all, he started out with all the dreams every actor has. Growing up in Chicago, he joined the city’s celebrated Second City theatre company and played a variety of improv and scripted roles for four years. Tracey Ullman saw him in an improv show, he was cast in her sketch series and was also asked to do voices for a weird cartoon she was having around the ad breaks. Last thing he expected was that the one-minute toons would make his living.

“I didn’t even think that four or five years into the show,” he says with a wry grin. “Then The Simpsons just kept going, and now it’s my bread and butter. But I didn’t know that was going to be my big gig.” He pauses, looks at me, then decides to make one thing clear. “Look, although I’ve talked about some frustration with The Simpsons, I think it’s the greatest job in the world. I’ve always loved cartoons; it has satirical writing; I get to play every role I’ve wanted to play; plus, financially it’s allowed me to do other things, like theatre, without worrying about pay – and to do interviews if it will promote these smaller things.”

In this case, “these smaller things” means his London theatrical debut, a curious blend of sketches, music and theatre called The Bicycle Men, which will be at the King’s Head pub theatre in Islington.

Castellaneta plays Steve, a hapless American tourist cycling through France, who winds up trapped in a village when his bicycle breaks down. He is insulted constantly, in that curious French passive-aggressive way.

Looking for somewhere to stay, he’s told to try the youth hostel but warned that he does look “very, very old”. He hands over his bike in the repair shop, and they say it will take six months. “I can’t wait six months!” he cries. “Okay, tomorrow,” they shrug. But, of course, tomorrow never quite comes. Outside, the puppet show plays scenes from his life, and shop-window mannequins attack him in a homicidal rage. It’s as if Kafka wrote Groundhog Day.

“The guys who created it are friends from the LA improv scene,” he explains. “Most of the Second City guys I performed with are in LA now. These three came up with the show at a regular Sunday-night slot and toured it to LA, New York and Chicago, but one of them couldn’t make the London run.”

Indeed, improv with his Second City friends is where he spends most of his nonSimpsons work time. He’s performed with his Bicycle Men buddies – Joe Liss, Mark Nutter and John Rubano – in shows such as Harold, where the gang improvise dialogue over old Harold Lloyd silent movies. He even sees the writing and playing instructions for Homer Simpson – “Do him like a dog trapped in a man’s body” – as similar to a classic improv comedy game.

“Because we start with the voice track on The Simpsons, we can improvise lines and pauses, and the animators get inspired by watching us in the recording,” he explains. “They sit and watch our faces to get a feel of what to animate. In fact, it’s much closer to improv than most of the TV, stage and film work I’ve done, which is strange, considering it’s a toon.”

Outside this, he’s using his wordplay skills to develop a writing career. With his wife, he’s penned a couple of Simpsons episodes, and the two are now finishing a comedy musical based on the Spanish-American war of 1898. Seriously.

“We wanted to draw comparisons between what happened then and what’s happening now,” he grins. “That war started with the explosion of the battleship Maine in Havana harbour, which the press whipped up into antiSpanish hysteria. We invaded Cuba and gave it independence, then stationed soldiers in the Philippines, where we ended up in a five-year battle against insurgents.

But, yes, for people to come and watch this, it has to be really funny and broad and satirical.”

And in his desire for satire he parts company with the fat, lazy Springfield guy for good. You would never hear Homer say, “I’m more or less a leftie. The Simpsons is immensely satirical – although its major thrust is that it’s written by guys who hate television, and this is their way of getting back at it. But also, at times, they make political statements, and I’m of that bent. After all, there’s so much fodder for it in America right now – you just pick it up, it’s like gold.” Homer’s critique, of course, would be – well, you know.

The Bicycle Men, King’s Head, N1, from Nov 6; www.kingsheadtheatre.org

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