4 Reasons Why Jimmy Fallon's First 'Tonight Show' Killed It

Fallon's first night included pop-ins from Lady Gaga, Mariah Carey and Kim Kardashian.

Now that is how you make your "Tonight Show" debut. After weeks of hype, endless commercials and interviews, Jimmy Fallon took over the biggest name in late night TV like a boss on Monday, kicking off his tenure with more stars than some shows have in a month.

Yeah, Will Smith dropped by to do the Stanky Legg (and tons of other moves) and U2 played a spectacular rooftop set (and a special unplugged tune), but it was the impressive list of other superstars who just dropped by to say 'hi' that proved Fallon is in for a smooth transition into his new gig.

Here are four reasons why Jimmy just killed it Monday night:

The Opening Monologue

Bringing the "Tonight Show" back to New York for the first time in four decades, a calm-looking Fallon got any weirdness out of the way first, joking, "I'm Jimmy Fallon and I'll be your host ... for now."

And, in a second rapid-fire friendly dig at his predecessor, the 39-year-old comedian thanked all the hosts who came before him, including Steve Allen, Jack Parr, Johnny Carson, "Jay Leno, Conan O'Brien and Jay Leno." And, after giving his mom and dad, Jimmy and Gloria Fallon, a shout-out, he apologized for not getting them better seats for his first night.

People Owe Him Money, Important People

In one of the night's best gags, Fallon confessed that most of his celebrity friends had bet him $100 that he'd never get the "Tonight Show" gig. That began a cavalcade of awesome, which included Robert De Niro, Tina Fey, Joe Namath, former mayor Rudy Giuliani, Mariah Carey (who pulled a hundy from her bra), Tracy Morgan, Joan Rivers, Kim Kardashian, Seth Rogen, Lindsay Lohan, Sarah Jessica Parker, Mike Tyson, a leotard-wearing Lady Gaga and late-night rival Stephen Colbert, who paid his bet off with a pail of pennies.

"Welcome to 11:30, bitch!" Colbert yelled after taking a selfie.

Two Words: Stanky Legg

Reviving one of his most beloved skits from "Late Night," Fallon got together with first guest Smith for "The Evolution of Hip-Hop Dancing." Wearing matching denim overalls, with one snap undone, of course, the pair ran through some classic moves, including: the Cabbage Patch, Running Man, Robot, Pop and Lock, Wop, Kid 'N Play, Biz, Hey Ho, MC Hammer, Humpty Dance, Spank That (which Smith got a bit too excited about), Dirt Off Your Shoulder, Making it Rain, Crank That, Stanky Legg, Dougie and the Carlton.

They also busted out some lesser known moves, such as: The Steal the Face (and swallow it and throw it back up), I'm About To Break Dance, Leg Thing No One Can Do, the Beastie Boys tribute Fish Eye and the post-Making It Rain dance Picking Up The Money Because That's All You Had.

But when Fallon started twerking, Smith had to call off the jam.

U2 Hit The Roof

It's one thing to have one of the biggest rock bands in the world on your debut. But it's another to have U2 play "Invisible" on the roof of 30 Rock 70 stories up with the lit-up New York skyline shimmering in the dusk light all around them. Performing for a small rooftop audience, the band played their new single with the assistance of a marching band drum corps and horn section.

As a bonus, U2 also did a special unplugged version of their Oscar-nominated tune "Ordinary Love" from the "Tonight Show" couch at Fallon's request. See? We told you he was a boss.

And he's just getting started, with a first week that includes such guests as Gaga, Bradley Cooper, Kristen Wiig, Jerry Seinfeld, First Lady Michelle Obama, Will Ferrell, Arcade Fire and, on Friday, Fallon's bromance-in-chief, Justin Timberlake