Idea of reliving youth sold Jonah Hill on "Jump Street"

Sincerity is not necessarily what you'd expect from the executive producers of a comedic riff on "21 Jump Street." The late-1980s hit TV series famously featured Johnny Depp, Richard Grieco and Holly Robinson as cops working undercover in the harrowing teen environs of high schools and colleges.

Earnestness is also not what you'd expect from those same producer-stars who greet you in a downtown Denver hotel suite wearing bicycle patrol uniforms.

On one heckuva blustery day recently, Jonah Hill and Channing Tatum were clad in short sleeves, black bike shorts and short-fingered gloves, just like their characters Schmidt and Jenko before the underachieving rookies are drafted for an undercover assignment in a high school.

"We're just doing a little work here. Keeping you safe," Tatum intoned as he entered the room. "If we could have brought our bikes, we would have."

Funning aside, the duo proved rather serious about their unexpected partnership, their careers, their adventure in producing.

Cracking wise isn't the norm for Tatum. Which is why Hill — the nudger in this undertaking — approached the former stripper turned model turned gainfully employed, endearingly committed actor in the first place.

"I knew I didn't want the other person to be known as a comedic persona. I wanted it to be myself and an action star who hadn't done a lot of comedy," said Hill, sipping a soda and ignoring a saucer of brownies and cookies a publicist set down.

"Channing has this great metaphor. It's like the eighth bite of steak — if it were me and another comedy guy. You've seen that before. You know what it tastes like. It's good. But it's steak. We wanted to have a combination that felt really fresh."

So Hill cold-called Tatum, best known for action and tear-streaked romance .

"I loved 'A Guide to Recognizing Your Saints,' " said Hill of the Sundance award-winning drama that reaped Tatum breakout recognition in 2006. "It's one of my favorite performances, ever. It felt to me — and I'm not just saying this because he's sitting here — it felt like a 'Mean Streets' type of performance. One of the rawest performances I've ever seen."

Tatum still credits writer-director Dito Montiel — for whom he also did "Fighting" and "The Son of No One" — with his love of acting.

"He ushered me in. He made me really care, made me dare myself. His honesty level is brutal," he said.

It was important to Hill that someone have his back, "who was protecting what I was really going after from the get- go," said Hill, who conceived the story with screenwriter Michael Bacall ("Project X"). "We could put a bubble over what we were trying to make, which was an R-rated 'Bad Boys' meets John Hughes movie."

Hill admitted having misgivings. It was his agent who suggested the project.

"I rolled my eyes like anyone would about turning a television show into a film. It wasn't something I aspired to or was interested in."

The idea of making a film "about guys who got to relive the most important and affecting period of their youth," Hill offered. "Thinking you have all the answers but going back and realizing you have none of the answers. And all your insecurities immediately revert back to when you were 17. That's a fun, fascinating and ripe idea for a film. "

Last year Hill developed quite an appreciation of the power of the unexpected. In a departure from the raunchy shenanigans of "Superbad" and "Get Him to the Greek," he portrayed statistical whiz Peter Brand in the Brad Pitt-championed baseball drama "Moneyball."

Hill and Pitt were nominated for Oscars for their work.

In light of that success, "21 Jump Street" might seem like a reverting to type for Hill.

Don't be fooled. The day after the Oscars, it was announced he'd signed on for the drama "True Story." Based on disgraced New York Times Magazine writer Michael Finkel's memoir about meeting Christian Longo, his imposter — and a murderer. The film co-stars James Franco. Pitt is producing.

As for Tatum, next up is director Steven Soderbergh's comedy "Magic Mike," slated for summer, in which Tatum plays mentor to a fellow stripper .

Then in a bit of director-swapping, he hopes to team up with "Moneyball" filmmaker Bennett Miller for a drama about brother Olympian wrestlers Dave and Mark Schultz. The former was murdered in 1996 by heir John E. du Pont.