The Freaks and Geeks creator turned comedy overlord has never hesitated to draw on the talent he assembled for his critically acclaimed depiction of high-school life in suburban Michigan, which aired on NBC for just three quarters of the 1999-2000 season before being cancelled.

Seth Rogen, who has appeared in six of Apatow’s big-screen productions (including starring turns in The 40-Year-Old Virgin and Knocked Up, and a blink-or-you’ll-miss-it part in Anchorman) since making his television debut as a foul-tempered Freak, has arguably benefited most from his partnership with the producer whose legend is growing faster than Ron Burgundy’s. But he’s hardly alone.

Jason Segel, another Freaks and Geeks alum, wrote and starred in this spring’s Forgetting Sarah Marshall. Martin Starr, who played a bespectacled, monotone misfit in the series, landed supporting roles in Walk Hard, Knocked Up and Superbad. And now, with the Apatow-produced Pineapple Express, it is James Franco’s turn.

Another former Freak, Franco earned his own big-screen breakthrough in 2002 as Harry Osborn, Peter Parker’s on-again, off-again best friend in the Spider-Man franchise. Even so, the recent UCLA graduate was eagerly anticipating an opportunity to revisit his lighter side – and to work with his old friends.

“Judd told me, ‘I miss funny Franco,’” he says. “I was definitely waiting for that.”

“For a lot of us Freaks and Geeks was our first big job,” Rogen adds. “It was a very exciting time in our lives, and we got to know each other really well. I think Judd and [co-creator] Paul Feig encouraged an improvisational environment, and because we all got along so well and bonded so much, we wanted to stick together.”

In Pineapple Express, Franco plays Saul Silver, a pot dealer whose desire to sell his product is rivaled only by his fondness for smoking it. The role was initially conceived for Rogen, who considered himself the ideal candidate to play an irresponsible layabout, much as he did in Knocked Up. Instead, Franco jumped at the chance to embrace a character so far removed from the serious-minded Harry Osborns of the world, so it was up to Rogen to play Dale Denton, the ambitionless office drone who likes to buy Saul’s weed.

Whatever the role, Rogen was on board from the start.

“Judd initially had the idea of a weed-action comedy, and he handed it off to Evan and I,” says Rogen, who co-wrote the film with Evan Goldberg after their successful collaborations on HBO’s Da Ali G Show and Superbad.

“We felt very personally close to the material. Guys smoking joints and shooting AK-47s? If the movie could integrate those elements in a comedy with a story you could actually care about, well, that’s the kind of movie I want to see.”

Although Rogen and Apatow would have to wait for Hollywood to grow comfortable with the concept of a mainstream stoner comedy – many studios initially passed on the project, citing concern over the film’s cavalier approach to drug use – the success of 40-Year-Old Virgin and Knocked Up ultimately earned them the green light. From there, it was a matter of fleshing out the script with actors who could thrive in the anything-goes atmosphere Apatow favors.

For Rogen, Franco and Foot Fist Way star Danny McBride, on hand as Saul’s backstabbing buddy Red, that sort of freedom was all part of the fun.

“On Superbad, Jonah Hill was very proud of how much he thought he improvised his part,” Apatow says. “When it came time for awards season, we had to transcribe the movie so we could send out the right script, and we realized that very little of the movie had been improvised at all. 

“Here, Danny, James and Seth improvised their parts quite a bit, and when an actor knows the other actors are allowed to change their lines, it alters the nature of the craft entirely. It keeps people on their toes. Sometimes a lot of script gets changed, sometimes none at all. In this case there was a very spontaneous approach to the filmmaking, and it worked.”