He's being hailed as the new King of Comedy, but it took a long time to become an overnight success, Knocked Updirector Judd Apatow tells Michael Dwyer.

BEFORE The 40 Year Old Virginopened in cinemas two summers ago, Judd Apatow didn't register high on the Hollywood radar. That gleefully risqué comedy became a surprise critical and commercial success, and Apatow has topped it with his second feature as a director, Knocked Up. Made for $33 million (€24 million), it earned almost five times as much in the US and some of the best reviews of the year.

One of the most entertaining comedies in years, Knocked Upoffers a refreshing spin on the genre staple whereby opposites attract. It throws together a newly appointed E! Channel presenter, (Katherine Heigl from Grey's Anatomyin a star-making performance), and a slacker slob (the unexpectedly endearing Seth Rogen). When she becomes pregnant after a drunken encounter with him, the consequences are coarse and raucous - and unexpectedly touching and emotionally involving.

Apatow's latest film as a producer, Superbad, which opens here next month, is the current US box-office champion.

Although the media routinely dub him the "King of Comedy", Apatow, who will turn 40 in December, has hardly been an overnight success, having toiled in the comedy vineyard for two decades.

"No, it hasn't been that easy," he admits during our recent conversation in Dublin, "but I've been very lucky that I've had jobs for a long time and worked with people I like. I just hadn't had that many moments when something I worked on was successful. Back in 1993 I made The Ben Stiller Show, a TV sketch show, when Ben was not well known, but we were cancelled after 13 shows. Then we made a movie for Disney, Heavyweights, in which Ben played the bad guy, but it didn't do well."

While he watched his friends - Adam Sandler (with whom he once shared an apartment), Jim Carrey and Stiller - rise from obscurity to stardom, Apatow had to survive some hard knocks. He was denied a screenwriting credit on the Stiller-directed, Carrey-starring 1996 movie The Cable Guy, on which Apatow was a producer. He produced and worked as a writer on two TV series, Freaks and Geeksand Undeclared, which were shunted around in the schedules before they could find an audience, and then ignominiously dropped.

Was he ever tempted to give up? "No, because I was always allowed to make something else and I was always making a good living, although I would have liked to have had a hit at some point. I got hired to do a lot of rewrites on movies - for Jim Carrey on Liar, Liarand Bruce Almightyand with Adam Sandler on The Wedding Singerand Happy Gilmore. But I was so proud of Freaks and Geeks. When it ended, I thought that if I never did anything again, at least I have accomplished that."

There were compensations, chiefly working on Garry Shandling's brilliant, caustically irreverent series, The Larry Sanders Show. "I was a writer on it for five years," Apatow recalls. "It was fun to do, and an amazing learning experience because Garry taught me everything he knows about how to create characters and how to write comedy. Most of what I do is based on things that I learned from him. He let me direct at the end of the series, and I ran the last season with a friend of mine.

"Garry is a genius, the best joke writer I've ever known. He's very brave about revealing himself. Writing Knocked Up, I thought a lot about how Garry's best work is confessional on some level. So I decided to take all my strange experiences regarding childbirth and my relationship with my wife, and to add that to all the stuff we fabricated and all the ideas I got from my friends and the actors in the movie."

Apatow encourages improvisation in rehearsal and on the set in what he self-deprecatingly describes as a "half-assed Mike Leigh" approach.

"I like to cast most of the actors before I write something and then discuss it with them along the way. While writing Knocked Up, I called Paul Rudd and asked him what his wife didn't like about him. He said she hated him spending so much time on the computer checking sports scores because he's in this fantasy football league. So I put that in that script.

"I talked to my wife and told her what the storyline is about. She said: 'Why don't you be a little tougher on yourself? You should do a scene where Seth's character is weird about having sex with her when she's eight months pregnant, the way you were with me. Put that in the movie.' And I did. It took me a very long time to find the courage to do personal work. It probably would have been impossible earlier because I had no life experience in my 20s."

He met his wife Leslie Mann when she auditioned for The Cable Guy. "I was reading with all the actresses," he says. "I remember coming out of the audition and saying to Ben : 'It is so weird that Mrs Apatow just walked into that room.' That's all it took, those eight minutes. And then I stalked her for several years."

His wife and their two young daughters are all in the central cast of Knocked Up. "I love working with Leslie because it's the only time that I'm in charge," he laughs. "At home I'm this normal castrated husband, but on set, she has to listen to me. We actually have a great time together. We have a similar sense of humour and she's a very daring, brilliant actress.

"She's hilarious, so there's no nepotism when I cast her. Her performances can be very revealing and even heartbreaking, and at the same time riotously funny. There's nobody who can do what she does. She's also the person who pushes me to make the female parts multidimensional and not just supportive of the men."

Joining Apatow and Mann in Dublin this week was Seth Rogen, now regarded as Apatow's screen alter ego. "It's funny, because there are a few guys who seem to portray variations on my problems and Seth is certainly one of them. He is brilliantly funny and he was just as funny when I first met him, when he was only 16 and he came to an open casting call in Vancouver for Freaks and Geeks."

I suggest that the ending of Knocked Up leaves the door wide open for a sequel. "Well, you never know," Apatow says. "I did television for a long time, so I like telling a lot of stories with the same characters. I'm not closed off to the idea of a sequel. We could even do it in 15 years when their kids are in their teens and yelling at them."

With a lively slate of movies on the way as a producer (see panel) and having scored such hits with his own first two movies, Apatow has set the bar high for his next outing as a director. "I know," he sighs, "and that's the beginning of creative paralysis, just thinking about that. Before I begin that process of making the next movie, I have to allow myself permission to fail miserably and then take some chances. I would like to make something different. I have some ideas, but they're all a little bit dark."

Does that mean Apatow is going to do a Woody Allen and turn all serious on us? "Well," he laughs, "the next one could be my Interiorsor hopefully, my Crimes and Misdemeanors, which is my favourite of all those movies."

Knocked Up opens today and is reviewed in this section.

Magnificent seven: Judd Apatow's been busy

Wearing his producer's hat, Judd Apatow is involved with seven movies for release in the months ahead and featuring what has become his unofficial repertory company.

"It seems crazy to have so many movies coming out," he says. "I'm not the main creative force behind most of them, but they reflect my taste."

I asked him to pitch them to Ticketreaders.

Superbad

Directed by Greg Mottola ( The Daytrippers)

"Seth (Rogen) started writing it with his friend, Evan Goldberg, when they were 13 years old. It took us seven years to get it made because it's a profanity-filled high school movie, but it's also very sweet and probably the funniest movie I've ever been associated with."

Walk Hard: The Dewey Cox Story

Directed by Jake Kasdan ( Orange County)

"It is a fake biopic of a Johnny Cash-type figure, played by John C Reilly, and it makes fun of Ray and Walk the Line and all those music biopics. Jack White from The White Stripes plays Elvis and The Beatles are played by Jack Black as Paul McCartney, Justin Long as George Harrison, Jason Schwartzman as Ringo Starr and Paul Rudd as John Lennon. We've got 33 original songs in it."

Drillbit Taylor

Directed by Steven Brill ( Little Nicky, Mr Deeds)

"It's based on an idea by John Hughes. Seth wrote it with our friend Kristofer Brown, who was the head writer on Beavis and Butt-head. Two kids are getting bullied at school and they hire a bodyguard played by Owen Wilson. They think he's a former army ranger but he's a homeless guy planning to rob their houses."

The Pineapple Express

Directed by David Gordon Green ( Undertow, George Washington)

"It's not due out until next summer, although that could change. It's a pot action movie, like a demented Abbott and Costello picture. James Franco is tear-down-the-house hilarious in it. He plays a long-haired marijuana dealer and Seth is a guy who witnesses a murder, and the two of them go on the run. They're high the whole time they're being chased."

Forgetting Sarah Marshall

Directed by Nicholas Stoller ( Undeclared)

"Jason Segel, who's in Knocked Up, wrote it and plays a guy who goes to Hawaii when his girlfriend (Kristen Bell) breaks up with him. But she's there with her new boyfriend, a rock star played by Russell Brand, who was fantastic. He steals the entire movie."

You Don't Mess With the Zohan

Directed by Denis Dugan ( Happy Gilmore, I Now Pronounce You Chuck and Larry)

"I wrote that with Adam Sandler and Robert Smigel. Adam plays a Mossad agent who's tired of violence. He goes awol and moves from Israel to New York to follow his real dream - to be a hairdresser. Then people discover who he is. It's an insane action comedy."

Step Brothers

Directed by Adam McKay ( Anchorman, Talladega Nights)

"We start shooting in two weeks. Will Ferrell wrote it with Adam McKay. Will and John C Reilly play 40-year-old layabouts. One lives with his mom and the other with his dad, and then their parents marry each other. It's like The Parent Trap starring 40-year-old idiots."

By Michael Dwyer