Not Jerry Seinfeld

“You wanna see the coolest thing in this whole place?” asks Jimmy Fallon, bounding down the hallway of the Saturday Night Live offices in a pair of big jeans. “Look!” He points at a wall of head shots. “There’s Chevy Chase, and John Belushi. That’s Eddie!” And almost everyone else who’s reinvented American comedy in the past 25 years. “Julia Louis-Dreyfus, Chris Farley …” On and on, till the last one: him. He raises his eyebrows and says, “It’s lunacy, right? Every time I see this, I totally flip out.”

You can tell how excited he is when he performs. He bites his bottom lip; his face threatens to crack into a smile – he almost lost it and laughed on the season premiere, imitating Jerry Seinfeld while sitting next to Jerry Seinfeld. The audience loved it. “The people who pop first on this show are the ones who you believe you can see right into their hearts,” says executive producer Lorne Michaels. “It was true of Gilda, it was true of John Belushi, and it’s true of Jimmy. You just feel you know them.”

Indeed, Fallon in person seems very much like Fallon on television – winsome, silly, ebullient. And why not? He has been dreaming up this life for as long as he can remember. Growing up in Saugerties, New York, Fallon would watch “the clean parts” of SNL that his parents taped for him, and then reenact the Wild and Crazy Guys with his friends and his sister. In college, he made a weekly ritual of drinking beer, eating chips, and watching the show by himself in his dorm. “Friends would be like, ’Dude, I’m having this major bash! I can’t believe you’re not coming,’ ” he says. “But I was like, no way. I missed the show once, and it was a really big deal for me.”

It was only a little over a year ago, when Fallon was studying at the Groundlings Theater in Los Angeles, making $7.50 for every set he performed at the Improv, that he was summoned to New York to audition for the show. “Everyone had told me, ‘Lorne’s seen everything, so don’t think you’re gonna blow his mind,’ ” he says. “But I did Seinfeld and Travolta, and then I did Adam Sandler, and when I looked down at Lorne, he was laughing.”

“I laughed for two reasons,” recalls Michaels. “First, it was really funny; second, Adam was a kid to me like five minutes ago, and that’s who Jimmy watched in high school! It’s like that joke, ‘I have ties older than this kid.’ Well, I have a show older than him.”

This summer, just before Fallon and SNL both turned 25, he was promoted from featured player to full cast member and finished a new Cameron Crowe movie. “I don’t know what my new goal is,” he says. “The cool thing about being 25 is that you still have leeway to goof off.” But dude, wouldn’t you say you’re pretty successful for a 25-year-old? “Well, look at Britney Spears. How old is she?”

Jimmy Fallon is in the adolescence of his fame. Being in your twenties is always partly about the strange gap between feeling that you inhabit a life you’ve created and feeling alarmed that you’re old enough to create one. But for Fallon, the awe of becoming a grown-up is compounded by the awe of becoming a star – and still feeling like a kid. You can almost see him flicker like a hologram between the sweet, small-town teenager of his past and the confident celebrity of his future.

Jim and his sister, Gloria, are the children of Jim and Gloria Fallon. (What’s up with that? “I know, right? What is up with that?”) His parents used to meet at block parties in Sunset Park, Brooklyn, before they moved upstate to raise the kids. But they weren’t sixties people. “My dad was in Vietnam, and he was in a doo-wop group. My mom was like a total square; she wasn’t allowed to leave her stoop in Brooklyn,” says Fallon, grinning. “She was a nun for about a month, but then she was like, ‘You know what? I didn’t get the calling!’ Ha! When did Sound of Music come out? I think there was like a thing where everyone wanted to be a nun.”

Unlike many comedians his age, Fallon says he had a happy childhood, aspires to be like his dad, and is extremely close to his parents and his sister, with whom he’s just written I Hate This Place: The Pessimist’s Guide to Life (TV Books; $7.95). “My sister studied writing and had all these scholarships,” he says. “She kind of got the brains in the family.”

Don’t be so sure. “His impressions are smart,” says Michaels. “You can do an impersonation where you get the voice right or the gestures, but he gets them the way Dan Aykroyd got some essential attitude of Tom Snyder – so you could never look at Snyder again without thinking of it.”

It’s almost unnerving when Fallon switches from his own guy-speak into an utterly precise mimicry of the voice-mail voice, or Gilbert Gottfried, or Nicolas Cage, because it reminds you that this isn’t just some silly goose: Nothing gets by him. Like Phil Hartman barking “You are correct, sir!” as Ed McMahon, Fallon seemed to be virtually channeling Chris Rock on a Conan O’Brien appearance last February: “Hey, Ma … Did anybody call for me? Gerard! Is he still on crack? Man, the last time I saw him, he told me I wasn’t eatin’ right. The man is on crack! I never heard of a healthy-conscious crackhead! I know the four food groups – ain’t one of ‘em crack!”

Later on in that program, Conan mentioned that Fallon is single, and the crowd started shrieking like crazed Beatles fans. “I was really embarrassed,” Fallon admits.

“I get the feeling with Jim that he’ll just find some girl and he’ll marry her,” speculates his friend and castmate Ana Gasteyer. “I think he’s flattered by his fans’ attention, but he’s really kind of honorable and old-fashioned in that way.”

The attention can be a bit much. Fallon is inundated with letters from enchanted young women, and the Internet is blooming with Websites like “The Jimmy Fallon Shrine” (“This page is devoted to the funniest sexiest most talented man in the known world!”), “Jimmy Fallon Is a Hottie,” and “Jimmy Fallon: Adonis!!” At his packed Barnes & Noble book signing last week, one 14-year-old from Pennsylvania had driven three hours with her family to lay eyes on him. “He’s perfect,” she said, looking very close to tears.

Asked how he feels about being “the hot one” on SNL, Fallon smirks and shifts around. “I’ve never really gotten this response before. I was never, like, the hot guy at the bar. I’m still not the hot guy at the bar.” Um, debatable.

Not Jerry Seinfeld