‘Knocked Up’ cast was quick on the uptake

Even comedy has its regular working hours, so July 26, 2006, was a typical day digging ditches on a Judd Apatow production. It was the 51st shooting day out of 56 on “Knocked Up,” the follow-up to Apatow’s surprise, $109-million-grossing hit, “The 40-Year-Old Virgin.”

The cast and crew were camped at a one-story house in Northridge that had been dressed as a bachelor/stoner/slacker playground: A lifeguard chair overlooked a ping-pong table in the driveway, the kitchen swelled with empty beer bottles, a “Fraggle Rock” poster shared wall space with porn star Sunrise Adams’ one-sheet in the living room, year-round red jalapeno Christmas lights were draped from the ceiling and two yellow chairs sat in a backyard pool half-filled with water the color of lichen. (It was actually iced tea.)

Like “Virgin,” “Knocked Up” is a sweetly profane romantic comedy built around a simple story line with a twist. A stoner layabout (Seth Rogen) and a career-minded beauty out celebrating her promotion to E! Entertainment anchor (Katherine Heigl) meet at a bar and have a one-night stand. Two months later, she discovers she’s pregnant, and the mismatched parents-to-be spend the next seven months dating to find out whether they even like each other.

But in Apatow’s creative alchemy, the distinctive crude-cute (crute?) tenor springs from the finesse of the story’s execution by the surrounding players -- Paul Rudd and Leslie Mann as a handy example of a realistic married-with-kids train wreck, and Apatow regulars Jay Baruchel, Jonah Hill, Jason Segel and Martin Starr as Rogen’s misguided Greek chorus (think college frat, not Aristophanes).

The scene they were shooting that day details the shattering moment when the guys learn that their big, long-developing business scheme, a pay website called “Flesh of the Stars” (you get the idea), already exists in the form of one “Mr. Skin.” The five friends stand around a computer desk alternately appalled, enraged, jealous, accusatory and blase. Apatow and Rogen hastily rewrote the scene that morning over breakfast when they realized that a sequence they had already filmed would have made the original version redundant.

In the disheveled living room, the walls were covered with primitive mock-ups from their website design, featuring naked breasts and vulgar slogans. Scrawled on a chalkboard across from the desk was: “TO SUCCEED WE MUST SMOKE WEED!!” Enormous Port-A-Cool 2000 fans blew cool air through the house using two-foot-wide bendy yellow tubes. (All day, the crew got updates on a brush fire threatening nearby Benedict Canyon.)

Apatow, with a scant beard, prowled the set in a pink-and-orange-striped rugby shirt, khaki shorts and sneakers. The on-set “Knocked Up” icon -- a martini glass with a pacifier looped around the stem -- adorned director’s chairs, shirts and paperwork. The cast, including the stocky Rogen in camo shorts and green Army T-shirt, burned through a straight version of the scene.

And then the fun started -- the rat-a-tat-tat improvisational back and forth between director and actors, which Apatow shot with multiple cameras precisely so the actors would know they’re allowed to overlap and change things here and there without causing continuity problems.

After Segel ran through some lines, Apatow, seated around the corner at a bank of monitors, said: “Jason, do it with real concern. Maybe that’s a little too flowery. Just reword it so it feels a little more real.”

As they worked through the scene, Apatow’s young, pop-culture-saturated troupe started throwing out an endless stream of references to film, TV and sports celebrities, with Hill displaying a savant-like ability to devise increasingly funny and clever slams of living famous people one after another.

They would burn through an entire 1,000-foot film roll just messing with the contours of the dialogue, much of which would never make the final cut. In between changing the rolls, Apatow wandered onto the set and brainstormed new comic options with the actors until Rogen genuinely giggled and said, “That’s funny.”

Finally, with the crew cracking up, Apatow chimed in: “You guys could literally end your ability to work with anyone in this industry in this one scene.”

As the 39-year-old writer-director ran the set in nearly triple-digit heat, it was obvious that he was willing to push his actors for hours, through roll after roll of film, until they said something very, very funny. “I don’t care how many jokes I have to get the actors to tell to get to the two that audiences remember for the rest of their lives,” said Apatow, pulling a stick of gum from a large baggie dangling off the back of the monitors.

They kept reworking it, changing details and lines, adding and deleting, tweaking the group dynamic, varying the tone. It was a straight hour of improv.

“When it’s a billion degrees it’s not that easy,” Rogen joked later. “For me, [improv’s] the easiest way to do it, because I have a hard time when I’m just told to do one thing over and over and over again. It’s my favorite way of working. You never know what he’s gonna tell you to do, and you know that you can try doing anything.”

Apatow pointed out that the “You know how I know you’re gay?” exchange between Rogen and Rudd in “Virgin” -- which became one of the movie’s signature, oft-repeated bits of dialogue -- was actually a random improvisation on set. The filmmakers had no idea anyone would think it was that funny.

“It’s tricky with a lot of guys being funny together,” Apatow said. “It’s very hard to capture the energy of men joking around with each other if it’s completely scripted. You just feel its stiffness. It’s very hard to fake laughter, the way you laugh when a friend says something crazy.”

Of course, it makes it easier when all of your actors are actually friends. In a variety of combinations, Baruchel, Segel, Rogen, Hill and Starr have worked together on “Virgin” and Apatow’s canceled underdog TV shows, “Freaks and Geeks” and “Undeclared.” In fact, Rogen has lived with both Starr and Baruchel, which is why the rapport on set and on screen feels so real.

“It feels like we’re just hanging out a lot of the time,” Rogen said.

“A few years ago I realized that no matter how unique you try to be, these are all the same stories,” Apatow said. “The only thing that anyone brings to it is their specific texture and the small details of their personal experience. And that has made a big impact on my work and my writing. It’s all in those very small shadings.”