"It's like a clown car in here!" Amy Ozols declared. The producer of NBC's "Late Night With Jimmy Fallon," and, next year, "The Tonight Show" pokes her head into the Fallon Band Room, a small space with a banjo and framed covers of Rolling Stone on the walls. The space looks accommodating when empty, but becomes quite snug when Jimmy Fallon, Robin Thicke and eight members of the Roots settle into it armed with toy xylophone, kazoo, cowbell, wooden block and a shaker that looks like a banana. To add to the tumult, they are joined by an assortment of makeup and tech crew members who slip through the door separating the room from the sixth-floor hallway at the 30 Rockefeller Center headquarters of NBCUniversal.

The group is taping a rendition of Thicke's hit song, "Blurred Lines" -- played entirely on instruments one might find in a kindergarten classroom -- as a "cold open" for the Aug. 1 edition of "Late Night." This sort of thing has become one of the show's signature segments. After several run-throughs without the singer in the room, Fallon and the band are getting physically warm. Spirits are high, even when the assemblage realizes the word "bitch" ought to be removed from the lyrics (Fallon will put his hand over Thicke's mouth at the right moment). The effort is offbeat, but not without charm: The scene has notched more than 8.8 million views via YouTube as of Aug. 14, a far bigger crowd than the 1.8 million that watched that episode of "Late Night."

"It feels like a party," said Ozols, days after the "Blurred Lines" segment went viral. "We don't make fun of things that we don't like. We celebrate the things we do like. That's Jimmy. That's what sets us apart."

NBC hopes that kind of esprit de corps will fuel Fallon's clown car as he drives it into new and probably rocky terrain next year.

Fallon is the designated heir to the throne of "The Tonight Show," the latenight institution that started with Steve Allen in 1954. After what is expected to be the ratings bonanza of NBC's Winter Olympics coverage in February, and after Jay Leno signs off from the program -- again -- the top-rated position in latenight will be Fallon's to lose. It's an understatement to say that the pressure is on for the new host, a veteran of "Saturday Night Live" who is nearing his 39th birthday. He's had a rocket ship of a career, having joined "SNL" in his early 20s. His move to "Late Night" in 2009 was deemed much smoother (and less scrutinized) than the transition of a then-unknown comedy writer named Conan O'Brien when he took over the post from David Letterman in 1993.

In addition to being tapped for the latenight big leagues, Fallon took a big leap in his personal life when he and his wife, producer Nancy Juvonen, became parents this month with the birth of their daughter, Winnie. Fatherhood, he said, has left him tired but very happy.

SEE ALSO: Jimmy Fallon's Greatest Hits (Videos)

Fallon's cred with the digital demo is one reason NBC is orchestrating the "Tonight" transition now, even as Leno retains his ratings advantage in the timeslot. Much has been made of the youthfulness of Fallon compared with Letterman and even Jimmy Kimmel, though it's noteworthy that Johnny Carson was actually younger than Fallon is now when he took over "Tonight" from Allen's successor, Jack Paar, in 1962.

Fallon has taken pains to avoid the snark and attitude of some of his competitors. His version of "Late Night" finds its voice in the many Internet-friendly sketches that migrate quickly online, according to Mike Shoemaker, who has supervised "Late Night" under Fallon's tenure. He cites as a prime example a silly bit called "Jersey Floor," a parody of MTV's "Jersey Shore" in which Fallon and show regulars answered the unasked question, "What if I were on that show?"

"He approaches it as a fan," Shoemaker said. That Everyman approach is sure to be part of the pitch NBC will make to auds in selling Fallon's move to "Tonight" in February.

With his grounding in sketch comedy, Fallon is a skilled impressionist who can range from President Obama to Tom Brokaw. And he can hold his own musically on stage. Some of Fallon's antics -- getting Bruce Springsteen to dress up as a 1970s version of himself; convincing President Obama to "slow jam the news"; and persuading actor Mark-Paul Gosselaar to play Zack Morris, the lead character he once played on "Saved by the Bell" -- have been viewed as significant coups.

"I haven't been diagnosed, but I'm assuming I have some type of ADD or something, where I love to just think of the next idea and do something and then do that, and do that," Fallon said.

What Fallon can't do, however, is control viewership patterns and corporate fortunes.

Latenight is a vastly different arena than it was under Johnny Carson. Once a kingdom, the daypart is now divided into fiefdoms, with competition not only from Letterman and Kimmel (whose move to 11:35 p.m. this year accelerated NBC's "Tonight" succession planning) but also Jon Stewart, Stephen Colbert, O'Brien and Chelsea Handler. Arsenio Hall, who made a splash late in Carson's tenure, is launching his latenight comeback effort in September.

"Latenight is a daypart that has seen significant erosion, and we are predicting comparable ratings across next year," said Jay Baum, exec veep and director of national video at ad agency Deutsch. "I don't think there is a significant expectation of big improvements at the 11:30 timeslot for NBC."

Fallon seems prepared for the inevitable speculation that comes with a move of this scope.

"There will be great ratings and then the Olympics will end and the ratings will go down and then there will be two months of 'Is he struggling? Is this not struggling?' And then we'll see how it ends," he said. "I think it's going to be fine."