PASADENA, Calif. -- He's not LL Cool J the rapper. He's LL Cool J the actor.

"This isn't my second job," he insisted.

"My focus is NCIS: Los Angeles. I take this very seriously. I'm committed to it.

"I started to wear my big clock, but I thought that wouldn't work."

Guess it was just "time" for a career change.

In fact, joining the cast of the new series NCIS: Los Angeles, which will air this fall on CBS and Global, in some ways has allowed the 41-year-old LL Cool J to feel like a kid again.

"It's really exciting for me to finally be doing something where I'm actually, like, new," he said. "I'm not like the elder statesman of hip-hop walking into the room. I'm actually an unproven guy that's trying to make something happen for you guys, and that's a great dynamic for me.

"So I'm a part of a team now. This is not LL Cool J solo on the microphone, you know, ripping his tank-top off. This is Sam Hanna, the former Navy SEAL."

At that point cast-mate Chris O'Donnell couldn't help chiming in, "How about for sweeps week?"

"For sweeps week, we might do a few things," LL Cool J said. "Some Eminem covers for (O'Donnell), too. We can work on those."

NCIS: Los Angeles is a spinoff from the original NCIS, which itself was a spinoff from JAG. The so-called pilot for NCIS: Los Angeles aired last spring, as a two-hour crossover episode that included the casts of both shows.

"I would like to just thank the original NCIS cast," said LL Cool J, who has acted in a few movies and some sitcoms but is entering new territory as a lead actor in a TV drama.

"Mark Harmon and those guys deserve mention and some respect. I had a great conversation with Mark, and he embraced me and was very, very nice to me, and us, on the pilot. This is their sister show and we want to try to keep the franchise alive."

In a TV landscape that has far more valleys than mountains, NCIS: Los Angeles generally has been tagged with the expectation that, well, if anything is going to be a hit in the fall, this might be one of the better bets. Certainly, LL Cool J and O'Donnell give the program instant recognizability.

"I think the main thing for us is just approaching it with humility and being clear that nothing is guaranteed and that our job is to do the best work we can," LL Cool J said.

"Obviously, we want to maintain the current NCIS fan base and (hook) all of those people that are joining the show. We don't want to make them have an allergic reaction to what we are doing on screen.

"The pressure part of it? I don't think anyone here is being arrogant. We are not making any guarantees or predictions for the playoffs."

LL Cool J added that the hardest part of taping a TV series doesn't have anything to do with the craft of acting versus the craft of rapping.

"For me, the biggest challenge in this whole situation is just staying away from the (catering) table," LL Cool J said.

"If I could just do that -- the candy bars, the doodles, the snicker doodles, the sugar cookies. Those hot warm doughnuts melting in your mouth early in the morning, while the crew is walking around and giving you plumber's pants (i.e., bending over and showing too much butt). It drives me insane."