Jimmy Fallon just wants to have fun

After a bullish staff meeting (which ended with a cheer) and before a wardrobe fitting (strictly suit-and-tie), Jimmy Fallon took time to marvel at how busy he is these days.

“The busiest I’ve ever been in my life,” he tells a visitor to the new “Late Night with Jimmy Fallon” offices at NBC.

“It’s ‘SNL’ times three. Times five. Times 10!” says the former “Saturday Night Live” cast member.

Come Monday, he’ll claim the weeknight 12:30 a.m. slot chartered in 1982 by David Letterman, then, in 1993, bequeathed to Conan O’Brien.

As Fallon speaks, he seems to hover more than settle in his chair in his seventh-floor corner office. Happily wired, he notes with amazement that, with so much to do, it’s almost noon – “and the next thing you know it’s midnight and you go, ‘I hope my wife’s not mad.’ ”

As if anyone could be mad at Jimmy Fallon. At age 34, he’s puppy-dog enthusiastic, funny and cool in an unassuming way.

It’s an engaging blend that kept viewers tickled for six seasons on “SNL,” where he scored with impressions of Jerry Seinfeld, John Travolta and Justin Timberlake, and created recurring characters like Nick Burns, the know-it-all tech-support guy. He has appeared in films including “Almost Famous,” “Taxi” and “Fever Pitch.”

Then, last spring, Fallon was tapped by “Late Night” executive producer Lorne Michaels (his former “SNL” boss) to return to the halls of 30 Rock, this time as host of his own show.

The idea had been broached long before, when he was exiting “SNL,” Fallon says.

“Lorne was like, ‘Keep in mind that Conan’s gonna need a replacement in 2009,’ ” he says. “This was in 2004. I said, ‘I don’t know.’ ”

Now Fallon is clearly putting his stamp on the venerable “Late Night” franchise. His house band is the acclaimed hip-hop group The Roots. Running the show is veteran “SNL” producer Michael Shoemaker, who handled “Weekend Update” when Fallon was co-anchoring.

And to help connect the show to a cyber-savvy public, “Late Night’s” co-producer is Gavin Purcell, who ran “Attack of the Show,” the daily Net-centric news hour on cable’s G4 channel.

In the spirit of the YouTube age, “Late Night” writers will shoot their comedy pieces themselves (“they can use me if they want, or not, but I’m available,” says Fallon), then edit them right in the office on Macs.

“We can be different and topical and fun,” Fallon vows.

Not that any of this strategy has been a state secret. For months, “Late Night” has been percolating in cyberspace with video blogs that offer an inside look at how a TV talk show germinates.

On his video blog, Fallon introduced to the world the show’s new logo – which viewers of that “vlog” had a hand in selecting.

“We’re not trying to ignore the fact that people are in front of a computer at work and surf the Web all day long, or that kids check the Internet when they get home from school,” Fallon says.

“We want to exploit that, and have fun with it. I’m on Facebook and I’ve been on Twitter just talking to my fans. It’s amazing!”

But there will also be guests who visit and talk with him, the old-fashioned way.

Scheduled for opening night is Robert De Niro, with others including Cameron Diaz, Serena Williams and Fallon’s former “Weekend Update” co-anchor Tina Fey soon to follow.

“I’ll also talk to scientists and chefs and animal trainers,” Fallon pledges with a grin.

He isn’t fretting about his competition – at least, not obvious rivals, notably CBS’ “Late Late Show with Craig Ferguson,” which, head-to-head against Conan, has been winning in total viewers.

No, the biggest challenge Fallon sees lurking is Mr. Sandman. The goal is getting viewers to tune in and hang with his show instead of hitting the sack.

“I need to be the Red Bull of late night,” he says.