LOS ANGELES - The Spanish-style mission resembles the courtyard of an upscale Mexican restuarant. At any moment, you expect a mariachi band to emerge from the wings, accompanied by a waitress loaded down with trays of guacamole and chips. Instead, the team that strolls out includes a best-selling rapper, an eternally youthful movie star, plus an Oscar-winning actress, all key members of the only guaranteed new hit of the new season. Of course, "NCIS: Los Angeles" could feature Moe, Larry and Curly and millions still would tune in for Tuesday night's premiere. That's because the drama is a spinoff of one of TV's most enduring and popular series, one that attracts more than 12 million viewers in reruns. It's also fortunate to immediately follow its big brother on the schedule, a position almost as cozy as a slot right after "American Idol."

The situation is a blessing -- and a curse.

"It's exciting to have the network behind you, promoting the show. But it does raise expectations," said co-star Chris O'Donnell. Best known for his work in "Scent of a Woman" and "Batman and Robin," he plays G. Callen, an agent so mysterious that no one, including himself, knows what the "G" stands for.

"My biggest concern," he said, "is to please the current 'NCIS' fans first and foremost."

That shouldn't be too difficult, seeing that the two shows share the same formula: Clean-cut military investigators use muscle and mischief to unravel complicated, tricky cases.

"At the core of 'NCIS' is that wonderful mix of drama, emotion and humor," said Shane Brennan, who oversees both shows. "For us to attempt to do this series without those three key ingredients would be crazy."

Brennan has taken pains to reassure fans of his juggernaut, itself a spinoff of "JAG," that the two projects are tightly related. Rocky Carroll will reprise his role as NCIS Director Leon Vance on an continuing basis and perky Pauley Perrette, who plays the forensics expert on the mother-ship series, will make a guest appearance as soon as next week.

What keeps the new series from being a carbon copy is the location. If Mark Harmon's character in "NCIS" had to work out of a chichi office like this one, he'd probably blow a gasket. In this series, however, the sun-baked facilities fit the bill. It's the new headquarters for the team that was forced to move after Callen was gunned down last season in an "NCIS" episode that served as the jumping-off point for this spinoff. The premiere picks up four months after that near-fatal shooting.

"It was always the idea that, on the outside, you have this old building, but on the inside you have this high-tech operations center," said Brennan, showing off the set earlier this summer. "It's a building that's undercover. It's a building that's telling a lie."

Keeping his shirt on

For "NCIS: Los Angeles" to have any long-range success, viewers will have to be impressed with more than the decor. The future hinges on the chemistry between the show's leads, which include rapper LL Cool J and veteran actress Linda Hunt.

"It's really exciting for me to be doing something where I'm actually, like, new. I'm not the elder statesman of rap walking into the room," said LL Cool J, author of the masterpiece "Mama Said Knock You Out," now trying to stay in rhythm as Sam Hanna, Callen's looser, stabler partner. "This is not LL Cool J solo on the microphone, you know, ripping his tank top off. I believe that teamwork is dream work."

Hunt's last-minute decision to play the squad's "numbers guy" is a little tougher to explain. The 64-year-old actress easily could bask in her past successes, including "The Year of Living Dangerously" and "Silverado," instead of signing up for what she calls the most grueling job of her career.

"I'm learning a whole new rhythm and timing, and I'm going to have to solve the problem of how to do things faster, as well -- and it's wonderful," she said. "You know, I've been living a life of a retired old person for quite a while, so perhaps I'll just change all of that."

Hunt's exhaustion level is understandable. Producers are opening the series with a bang. Make that bangs. There's lots of action, including an opening car chase that results in the discovery of a slain military officer, making the premiere even more high-octane than a sweeps episode of "NCIS."

Brennan admits they've pumped up the adrenaline to make sure viewers stick around for an extra helping of military-based whodunits. Even LL Cool J ripping off his shirt wouldn't help if "NCIS" diehards don't fully welcome this newcomer into the family.

"I don't think anyone here is being arrogant," LL Cool J said. "It's not like we're making any guarantees or predictions that we'll go to the playoffs. We just want to make sure that the 'NCIS' fan base doesn't look at what we're doing onscreen and have an allergic reaction."

njustin@startribune.com • 612-673-7431