"Neighbors"

Seth Rogen, left and Zac Efron, star in the new movie "Neighbors." (Carolyn Cole/Los Angeles Times / May 1, 2014)

A glance across the room at an awkward Hollywood awards show party first united Zac Efron and Seth Rogen.

"It was kind of a longing look," Rogen said, recalling their first conversation.

"You can't come out and say it, but I was like, 'Dude, I'd ... die to work with you,'" Efron said. "I was kind of imploring him. As a dude growing up in today's world, Seth is someone who I always really related to."

At 32, Rogen has built his career as an actor, writer and producer around an amiable slacker persona in such comedies as "Knocked Up" and "Pineapple Express." At 26, Efron built his as a heartthrob in the Disney Channel's "High School Musical" movies and in "Hairspray" and "17 Again."

In real life, these two young actors are also facing different stages of life: Efron, the buff, fresh-faced one, is recently out of rehab and trying to establish a career as an adult while Rogen, the R-rated comedy king and notorious pothead, is a busy, married producer of his own films.

Now (mostly) grown up and quite successful in their own ways, the two serve as each other's foils in "Neighbors," an "Animal House"-style comedy in which Rogen plays Mac, a sleep-deprived new dad forced to confront his changing lifestyle when Efron's Teddy and his hard-partying fraternity move next door.

The pair recounted their meet cute moment in an interview at the office of Rogen's production company, Point Grey Pictures, in a building on the Sony Pictures lot that used to house the studio classroom where Mickey Rooney and Judy Garland once studied. A large sex toy that was a key prop in Rogen's previous film, "This Is the End," sat on a shelf.

It was a fitting location for a conversation with dozens of uses of the word "dude," umpteen F-bombs and a fair amount of candor on the subject of maturity. For Efron, working within Rogen's man-boy realm was actually an opportunity for growth.

"Everyone's getting old with me," Rogen said. "One of the things I'm most happy about with ["Neighbors"] is that I'm able to be true to who I am as a person who is maturing and at the same time make a movie that is as immature as the rest of my career.... In real life I relate much more to my guy than his guy, which is a sign of the times man."

Rogen produced "Neighbors," which is directed by Nicholas Stoller ("Forgetting Sarah Marshall") and written by Andrew J. Cohen and Brendan O'Brien. The film — drawing positive reviews for the most part and expectations for fine business — also stars Rose Byrne as Mac's wife and accomplice, Kelly, and Dave Franco as Teddy's No. 2.

Initially conceived with Teddy as a clear-cut bad guy, the movie evolved to give the character more nuance, Rogen said, at Efron's behest.

"Zac was like, 'Frat guys have to like this movie,' and that honestly wasn't something that had occurred to us," Rogen said. "We were very much in the mind-set of, we're all nerdy, comedy writery guys. It's definitely in our instinct to explicitly villainize the frat. Zac came up with ideas of reinforcing brotherhood ... cause you know a lot of frat guys, right?"

Efron does, indeed, know a lot of frat guys, though neither he nor Rogen went to college. "I know a dude who is a lot like Teddy but who would take a bullet for me," Efron said. "And that was the fun part for me to examine was how seriously could I take these guys.... I wanted guys who are in fraternities to be like, '... yeah!' I hope every fraternity would be glad to see this."

On set, Efron slipped into the improvisation-based world of Rogen's films, where the director, writers and actors blurt out suggested punch lines.

"You have to be ready to hear brilliance and not break character," he said.

"Or not brilliance, mostly," Rogen said. "You just have to be ready to hear words and repeat them. Trust is the hardest thing people have with it. A lot of actors like to be really in control of their performances so even if the worst editor and the worst director of all time were making the movie, they would retain what they wanted to do."

"After the first scene we filmed I was like, I'm just gonna commit to something, but not know necessarily what it is," Efron said.

"Which is a good confident play," Rogen said.

Efron and Rogen both started acting as teenagers, and found fame playing characters on the opposite ends of high school's sociological spectrum: Efron, blue-eyed and square-jawed, was a jock heartbreaker in "High School Musical" and Rogen, Canadian-born, curly haired and doughy, a wisecracking outsider in the NBC teen comedy "Freaks and Geeks."

One of Universal Pictures' posters for "Neighbors" — the stars standing shirtless side-by-side — has fun with their dual images, one as the guy young women would love to date and the other as the guy young men would love to befriend.

Rogen's public persona is heavily intertwined with his recreational marijuana use. He has copped to smoking weed when he writes and appeared on stage at the 2008 MTV Movie Awards smoking a joint. But his career and personal life show no signs of having suffered for it. He is married to screenwriter Lauren Miller, his company has another film due this year, "The Interview," and he radiates a down-to-earthness that has eluded other comedians at his level of success.

"You have to participate in culture to participate in culture," Rogen said. "You have to watch the same shows people watch and go to the same movies and go out in the world and walk around and go to the grocery store and buy your own [stuff]. I'm very fortunate because I for whatever reason I'm not someone people are interested in from a celebrity tabloid capacity. I dodged that bullet completely."

For Efron, who was raised in central California, the public eye has been a more challenging place. Paparazzi have camped in front of his house for years, and that only worsened with his trip to rehab last year for drug and alcohol abuse. In March, he got into a fight with a homeless man in downtown L.A. in the early morning hours, an event he attributes to being "in the wrong place at the wrong time."

Working with Rogen, he said, had an effect he didn't anticipate when they met at that party, by challenging a single-minded career perspective that led him astray.

"I've learned a ton from Seth," Efron said. "A lot of the great things that happen around Seth are not performance. They're the kind of dude he is, the kind of friend he is.... Who you are is important. Very little of it has to do with your performance."

rebecca.keegan@latimes.com