When CBS' "Moonlight" premieres on Friday, Sept. 28, it may mark the first time that a 25-year-old American actor gets to take over a role originally cast with a 60-year-old born in Croatia.

But luckily for Jason Dohring, he knows a man named Joel Silver.

Hollywood heavyweight Silver ("The Brave One," "V for Vendetta," "The Matrix") is executive producer of "Moonlight," which stars Australian Alex O'Loughlin as Mick St. John, a vampire private eye in Los Angeles. Silver was also executive producer of Dohring's last show, UPN and The CW's "Veronica Mars."

During the pilot process for "Moonlight," CBS brought in David Greenwalt, co-creator of the "Buffy the Vampire Slayer" spin-off, "Angel," to restructure the original concept by Ron Koslow ("Beauty and the Beast") and Trevor Munson.

Greenwalt bowed out early for health reasons, but not before recasting just about every major role except O'Loughlin's. Rade Serbedzija ("24," "Shooter," "Snatch") moved out as 400-year-old vampire and hedge-fund trader Josef, and Dohring moved in.

"It was really cool that [Joel] called out of the blue and said, 'There's a role, and I'm making it younger'," recalls Dohring, speaking on his first day of work on the set at Warner Bros. Studios, in late July. "I read the two pages that they had. It's such a dark character. He was sharp. I was like, 'I get this guy. I get it.'

"I had to go through the process of audition and all of that. Even so, Joel pushed it all the way through to the end. I don't know if it would have happened [without him]."

Dohring sees some parallels between his "Veronica" character, high-school bad boy Logan Echolls, and Josef, and some important differences.

"This character is like Logan but even more extreme," he says, "which is fun to play. It's cool to keep going forward in challenges, as opposed to doing something you've done before. This is not like what I've done before.

"There's no little blonde girl, just a tall, dark, handsome drink of water."

Ironically, on "Veronica Mars," Dohring played younger than himself as Logan, but on "Moonlight," he's playing a bit older. And, although Dohring's the youngest member of the cast, Josef is the most senior vampire, a self-centered veteran of the night who's used to getting his own way.

"That's going to take some acting," Dohring says, "especially with Alex. That's the challenge right there, for me, keeping that there. But at the same time, Mick's more of a moral character, so there's some respect there in that regard, because I'm without that quality, the moral-ness.

"But, yeah, there is some authority, just age-wise, so that'll be the constant thing that I'm working on always, to make sure I keep that."

"Veronica" fans may notice that Dohring looks a bit bigger than he did then, but not too big -- not anymore, anyway.

"I actually got a little too big," he says, "because I couldn't move around as much as I wanted to. When you get muscled, it actually resists flexibility, so I'm doing stretching, working out with just my own weight, not the huge weights, but push-ups and pull-ups."

And Dohring gets to slip that upgraded physique into some very sleek threads.

"When I came in for my first fitting," he says, "it was Versace and Armani. There was nothing that wasn't high end."

Asked if he dresses like that in real life, Dohring says, "Yeah, I like fitted clothes. I like designer stuff. I've bought a couple $300 T-shirts. I still have them. They're fantastic. They're surprisingly plain, but they're very comfortable."

Since "Veronica" filmed in San Diego, a little over 120 miles south of Los Angeles, Dohring is enjoying working in Burbank.

"I love it," he says. "It's so cool. I live 15 minutes away. I just jump on the freeway and come over."

Shooting on a big studio lot is also a bonus.

"It's fantastic," Dohring says. "There's a cool feel around Warner Bros. It's very playful, lighthearted feel. You go in the cafeteria, and I felt like I'm Debbie Downer in there, everybody was so cool."

While some might wonder if the lot, founded in the late 1920s, might be haunted, Dohring says, "Haunted with good vibes. I don't ever get the sense that it's creepy."