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You’ve known this talk-show host and comedian from Saturday Night Live and Late Night. Now you know him from The Tonight Show. And you’re about to know JIMMY FALLON even better.

When I first meet Jimmy Fallon, he’s holding the door as I dash to the ladies’ room, bundled under 14 layers and my nose still running from the cold. His assistant walks me into his office two minutes later, and we officially meet. Jimmy’s dressed in a red cardigan, a white button-down, a tie and Converse sneakers. My first impression of the talk-show host, comedian, actor and musician is his striking resemblance to Mr. Rogers of Mister Rogers’ Neighborhood. But the resemblance runs more than sweater-and-sneakers deep. Like Mr. Rogers, Jimmy has an infectious enthusiasm and gets genuinely excited about even the most mundane things, making those around him feel the same way. In fact, he says “so fun” so much that it might as well be his own personal catchphrase.

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As it was for Mr. Rogers, religion has been an influence in Jimmy’s life. Mr. Rogers was an ordained minister before making his television debut, and Jimmy was an altar boy who once wanted to be a priest. Like Mr. Rogers, who voiced many of the characters in his “Neighborhood of Make-Believe,” Jimmy’s been doing deadpan impressions conceivably since he could speak. And like Mr. Rogers, Jimmy is someone who feels like a friend when we welcome him into our homes via our television screens — as host of NBC’s Late Night with Jimmy Fallon from 2009 until this past February and, following that, as host of The Tonight Show Starring Jimmy Fallon, taking the reins from longtime frontman Jay Leno.

A native of New York, Jimmy has moved the production back to the Big Apple, where Johnny Carson hosted the show for 10 years before moving it to Los Angeles in 1972. Aside from changing locations, Jimmy says he hasn’t materially altered The Tonight Show except for changing the time and bringing on an additional 50 to 100 staffers to make the production process smoother.

With the new job comes a new office, which already looks lived-in. It boasts an impressive oval conference table, where his sketch-brainstorming magic happens. A large flat-screen television is in the corner on mute, flashing sports scores. More than a dozen framed photos of his family are symmetrically hung around his desk. An acoustic guitar and a custom Dean guitar adorn the walls.

But, before the new office and the new show, Jimmy remembers how much he grew as a host during his stint with Late Night. “Imagine you have videotape of you working the first month at a new job,” he says. “Then you’re here five years later and you’re like, ‘Is that what I used to do? Is that how I used to act?’ I was so nervous. And you look back and think, ‘I shouldn’t have been that nervous; it’s all going to be fine.’ ”