When Jimmy Fallon first took his seat behind the desk of “Late Night” in 2009, the question on a lot of people’s minds was, “How in the world is the giggly kid from Saturday Night Live replacing the fiery, hilarious Conan O’Brien?” A similar question is now cropping up in the minds of “Late Night” viewers who are preparing for Seth Myers, another SNL alumni, to take Fallon’s spot. Certainly, a show that got its beginnings from an esteemed TV personality like David Letterman demanded a host who could hold his own and most people weren’t quite convinced. Fast forward five years and Fallon has become one of the most loveable late-night entertainers to dazzle the devoted insomniac populous in decades.

THE GOAL IS TO HAVE FUN

It doesn’t take Nancy Drew to figure it out. Fallon has wit, authenticity and originality all wrapped up in a debonaire suit, singing parodies with Justin Timberlake and jamming with The Roots. More than that, Fallon has become recognized as the every-viewer, with such humility that there’s no conceivable wall between him and his audience.

“My goal is just to make you laugh and put a smile on your face,” Fallon said during the cold-opening to his “Tonight Show” debut, “so that you can go to sleep with a smile on your face and live a longer life. … Isn’t that the whole goal of what we’re doing — to have fun?” What ensued was precisely that.

FRESH PRINCE AND TOP OF THE ROCK

Taking Fallon’s seat at “Late Night” is another SNL alumni, Seth Myers. Myers finds himself in the same spot Fallon did five years ago,

“The Tonight Show” is kicking off its first week with some all-star guests and live musical performances. Monday night, Fallon was joined by the Fresh Prince himself, Will Smith, to chat about life, the Olympics and his family. The two of them also performed a skit entitled, “Evolution of Hip-Hop Dancing.” U2 showcased their latest single, “Invisible,” to a small crowd on the world famous “Top of the Rock” at the very top of the Rockefeller Center, towering 70 stories over New York City. Later, the band came inside the studio to perform an acoustic-song-turned-jam-session with The Roots to close out the show.

SUPREME LINE-UP

The epicness doesn’t stop there. Tuesday night, Kristen Wiig and Jerry Seinfeld took their seats on the couch to banter with Fallon followed with a performance by Lady Gaga. Wednesday night featured Bradley Cooper and Tim McGraw. And Thursday night, the first lady Michelle Obama will sit down with Jimmy followed up by an interview with Will Ferrell and a performance from Arcade Fire. Then the whole week will wrap up on Friday night, featuring Fallon’s all-time favorite guest and musical act, Justin Timberlake.

OUT WITH THE OLD

There was a good bit of controversy surrounding “The Tonight Show” in 2010 when Conan O’Brien replaced Jay Leno, only for his job to be revoked and handed back to Leno after some pretty disappointing ratings. O’Brien’s audience tanked after a few weeks, at one point drawing two million fewer views than Letterman — which is why Fallon included in his opening bit, “Welcome! I’m Jimmy Fallon and I’ll be your host … for now.” Later he added, “If you guys let me stick around long enough, maybe I’ll get the hang of it.” Given all the celebrity cameos in his debut episode and his week of rockstar guests, Fallon clearly has a great deal of support on the showbiz end of things. However, time will only tell if he can keep the ratings high enough to carry the Jay Leno torch. Hopefully, we’ve learned something since the O’Brien debacle. Besides, we could all use a little more giggling in our lives.

Show Jimmy some love by tuning into “The Tonight Show,” weeknights on NBC at 12 a.m.