Actress Leslie Mann, who had a memorable if brief role in "The 40-Year-Old Virgin" as "the drunk girl," has a larger, meatier role in "Knocked Up" as Heigl's married sister. In real life, she's married to Apatow, and admits that his recurring theme might have some basis in reality.
"I remember driving in the car with him," she said, "looking over at him, thinking, 'This is the kind of guy I should be with. I would never be with him, but this is the kind of guy I should be with.' And then somehow, we went out again, and he kissed me, and then it was all good after that."
When asked if he was a geek in high school, Apatow joked, "I was, I dunno … who's to define geekdom? I liked comic books. Sure, I bought 50 books about the Marx Brothers. Used to tape 'Saturday Night Live' with an audio cassette player and transcribe it. Is that 'geek' in your world?"
At Syosset High School on New York's Long Island, Apatow used a radio show to interview comedians such as Jerry Seinfeld and Garry Shandling. It was about comedy for Apatow, never really about filmmaking, and he pursued stand-up and appeared on HBO's young comedians special in 1992.
Those roots in comedy have led to a loose, improvisational filmmaking style.
"You have to cast people that can improvise on their feet," Apatow said. "I want to take the handcuffs off of everything. So if I say to Katherine, 'Tell Seth that he got you pregnant,' the thing that I write is rarely going to be as good as the eighth thing Seth says when he's trying to be in the moment. … When you're shooting for 12 hours and you're really exploring the material, other things come up."
"I don't see it so much as improvisation so much as rewriting the script on its feet with the cameras rolling, at enormous cost to the studio," he joked.
Actor Paul Rudd starred in "The Forty Year Old Virgin" and plays Mann's husband in "Knocked Up." He says that Apatow "relies heavily on the actors," even when the cameras aren't rolling.
"He likes to cast the parts, if he can, before the script is even written," said Rudd, "and we'll talk about the character and maybe talk about certain stories or situations and work them into the script. We'll get together and improvise stuff and shoot it, and that will eventually sometimes make its way into the script. And then we're shooting it and there is a script. We'll oftentimes go completely off the script and its true improvisation. … It's great. It's so collaborative."
Apatow explained: "What I'm trying to do is collaborate with a group of people where we're all kinda giving it up, and it gets funnier and more real, because I can call Paul Rudd up and say, 'What does your wife hate about you?' So, it really is a group effort."
"But I will accept all the praise if that's possible," he joked. "In fact, maybe you can remove that part about other people doing things."
Apatow says that as a child he was fascinated by Paul Reiser in the film "Diner," because he heard that Reiser improved his lines. "That was always a seed in my head that that's something you could do," he said, "and when I started doing television and movies, I realized I should just roll a lot of film and get a lot of options. Again, it's a nervous way of working because you're assuming failure."
Hollywood is not assuming failure with Apatow these days -- he currently has eight movies in various stages of production.
"It's an enormous miscalculation," Apatow said. "I worked very hard and couldn't get any movies made, and then suddenly they said, 'You can make those movies,' and instead of saying, 'Let's spread that over, out over a decade,' I said, 'OK, let's, let's go,' and, and, it's bad."
The kind of bad most that most filmmakers can only dream about.