Hill and Tatum's unlikely comedic pairing

At first, Jonah Hill balked when he was offered the assignment of co-writing an R-rated comedy based on the show, 21 Jump Street.

He just couldn't see his way into a modern take on the TV police procedural that showcased Johnny Depp in his 1980s breakout role.

"I was like, 'Forget it, I pass,'" recalled Hill in Chicago recently to promote the movie with Channing Tatum.

After some persuasion by the studio, and creative sessions with writer Michael Bacall, Hill started to appreciate how a revamped adaptation might function.

"The goal was making it like a Bad Boys meets a John Hughes movie," said Hill. "And now I feel confident that we have some kind of cool version of that."

Opening March 16, 21 Jump Street is co-directed by Chris Miller and Phil Lord, and features Hill and Tatum as rookie cops assigned to go undercover by posing as high-school students in order to bring down a synthetic-drug ring. Co-starring are Ice Cube as the harried police captain and Rob Riggle as the overzealous coach.

The film, and the laughs, are mostly driven by the unlikely team of Hill and Tatum. Hill, 28, earned a recent Oscar nod for his co-starring role in Moneyball, but is mostly known for his foul-mouthed sidekick in Superbad, and as one of the rude friends in Knocked Up. Tatum, 31, is the handsome hunk type, and divides his screen time between action (Haywire) and romance (The Vow).

A raucous buddy flick is new territory for Tatum, but that's exactly why Hill thought the unlikely combination would work.

"I really wanted the pairing to feel unexpected," Hill said. "And I really wanted the movie poster to be like, 'Wow, I've never seen these two guys together.'"

For his part, Tatum was a little anxious about his role. Improvising in a flat-out laugh-fest is far from his comfort zone.

"You've got to give yourself over to it, in a way," he said of the improv approach that Hill favours. "And you have to have faith in Jonah, and the people that chose you, and go with it."

Along the way, Tatum said he felt he was "schooled in the art, because I can't imagine making a movie in this genre without the actors helping each other."

As it stands, Hill gives Tatum an A for effort in ad libbing. In fact, both actors agreed it was Riggle, as the out-of-control coach, who came up with some of the best lines.

"Rob Riggle is psychotically funny," admitted Hill. "It's like a medical issue."

Tatum said in one sequence involving the three of them that "all Jonah and I did was try to figure out a way not to laugh."

Riggle, memorable as the Tasering cop in The Hangover, said the 21 Jump Street environment "was freeing to the point of craziness," which encouraged him to go full throttle. "When you know the best line wins no matter what, it only makes things better, and funnier," he said.

Besides the Riggle bits, another of Hill's favourite scenes is the opening, when the actor goofs on his teen life in high school as a wannabe Eminem during the rapper's Slim Shady phase.

"I had that idea while we were shooting," said Hill, whose character struts into his school to Eminem's Slim Shady tune. "I had a lot of resistance from people on that, but I was like, 'Just trust me.'"

The moment sets the tone for the rest of the action-comedy ride, which includes a high-profile cameo.

"I wanted the movie to feel like an hour-and-a-half party," Hill said. "I wanted to have fun doing it, and the audience to have fun watching it, and I feel we deliver on that."

He also said he thinks the film connects on a level that the teenager in all of us can appreciate.

"I like our film's back-to-the-future element of reliving a really important period of your life," said Hill. "You know, that's when you think you have all the answers in high school, but then you find out all the answers are completely false."

So, when the undercover cops return to high school, "they revert to the insecurities they had when they were 17, because of their surroundings."

At the conclusion, there's even a hint that the buddy cops might be heading to college for a sequel. Hill and Tatum said they are willing, if movie fans show their support.

Meanwhile, Tatum said he has a proposition for Hill that might be a change of pace for him. In a few weeks, Tatum is doing a few re-shoots on his film, Magic Mike, set for a summer release. It recalls Tatum's brief stint as a male stripper.