On Friday, Apatow directs and produces "This is 40," a comedy he wrote centered around the family first seen in his 2007 hit "Knocked Up" - Debbie (played by Apatow's real-life wife Leslie Mann), her husband Pete (Paul Rudd) and their two children, played by Mann and Apatow's actual daughters, Iris and Maude.

Five years on from the raunchy pregnancy comedy, the new movie shows Pete and Debbie struggling through the ups and downs of marriage, parenting, work and finances now that they have entered their forties.

Apatow, 45, sat down with Reuters to talk about how his real-life family inspired a film he calls "a fabricated mutated version of our lives."

Q: Did you always know you would revisit these characters down the road?

A: "No, there was no part of me that considered it at all. I was pushing for the 'Superbad' sequel hard, but I couldn't get anybody to go for it. Then after I shot 'Funny People,' I started thinking about how many strange things were happening in my house. There were so many tensions, the girls were fighting, Maude started junior high school and there was so much happening emotionally.

"In the middle of the night it hit me: Pete and Debbie. And last we saw Maude, she was a little girl who didn't understand how babies were born and now she's a teenager."

Q: This project was a family affair. Was it important to have your wife and kids involved?

A: "Yes. The key for me was that 3/4 of the family was a real family so when they looked at each other, you could tell they love each other or they're hating each other and the emotions are very real. I have a pet peeve about kids in movies in that it's very rare that they seem like a family. I knew that if I did my process with my family and my children, something really alive would come out of it."

Q: You're 45 years old and your wife is 40. You probably could not have explored these themes earlier, right?

A: "I did this movie right when it was happening in my life. In a lot of ways, I'm just tracking my life. I did (the TV show) 'Freaks and Geeks' while I still remembered high school. And in a lot of ways, 'Knocked Up' is that period right after college of people not being sure what to do and dealing with how mature or immature they want to be."

Q: Would you say this movie is your most mature film to date?

A: "I don't know. I never think of it in those terms. I think in a lot of ways, nobody wants to be mature. I go visit my grandmother in a nursing home - she's 90 - and they all have the same issues: who sits where in the cafeteria, the cool people at one table ... The whole idea that anyone is mature, I think is a lie. Anyone who puts that facade of having their act together, I find is the first person who gets in trouble doing something in secret."

Q: Your wife has appeared in many of your films, but this is her largest on-screen contribution. Do you cast her because it's convenient, or because she's the best for the role?

A: "Sometimes I think, could someone else play this part? Am I doing this with Leslie because it's Leslie? I'll try to run the names - who would I have cast if it wasn't Leslie? And I can't think of anybody. There's zero people on that list who act that well, are that emotionally vulnerable, who could play comedy and drama simultaneously in the same scene, who go that deep. So that's the appeal for me: knowing someone that intimately who's so amazing at what she does, and then makes a gigantic writing contribution."

Q: What kind of writing contribution?

A: "With these movies, I don't write them and hand them to Leslie. They're written with her as my partner. I'm telling her the idea before I start writing and she'll say, you should talk about how good it feels when strangers hit on you, or you could do a scene based on that time the hockey team hit on me and my friends. That's the kind of collaboration that you can't get from someone you're not intimate with."

Q: What makes the two of you click on that level?

A: "Leslie comes at this as an actress. Being around her, and what interests her, has drawn me towards something that's more truthful and goes deeper. Her wanting to put herself out there completely makes me want to put myself out there completely."

Q: Will we see more of Debbie and Pete and their kids?

A: "I like the idea of it. If you said to me that 40 years from now there were five movies that track the arc of their lives, that would be the greatest thing ever. So I don't know if we'll do it, but I'm not closed to it."

(Editing by Jill Serjeant)

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