Lady Gaga's career came full circle for a moment Friday night. The singer headlined Z100's annual Jingle Ball concert at Madison Square Garden, an event that holds special meaning to the New York native. "This was the first live show I ever went to -- whose first live show is this?" Gaga asked the sold-out, tween-heavy crowd. "I used to listen to Elvis Duran every day on the radio and imagine how one day he would be introducing my songs."

Slideshow: Concert Highlights From Z100's Jingle Ball

As she strapped on a custom-made Christmas-tree shaped keytar, Gaga reflected on her first performance at the Jingle Ball just three years ago in 2008. "I'll never forget it -- there were a whole bunch of superstars here and nobody knew who the hell I was. And this song had just started playing on the radio," she said before playing her first single "Just Dance."

Her 40-minute set included current hits from her album "Born This Way" -- "The Edge Of Glory," "Judas," a half-piano version of the title track -- which became Billboard's 1,000th No. 1 in February -- and a hospital gown-clad "Marry The Night" finale that paid tribute to her recently released 14-minute music video.

Billboard hit the red carpet and spoke to LMFAO, Karmin, Hot Chelle Rae and others. Watch:

Other hits included  "Bad Romance," "Telephone," "Poker Face" and a reprise of her performance of "White Christmas" from her "Very Gaga Thanksgiving" special in which she added her own extra verse. "This song's too short… Just when I get into it, it stops. It's like a really bad orgasm." Instantly knowing she made an R-rated joke at a PG show, Gaga then growled, "Merry Christmas, New York!"

Gaga capped off a night that also included performances from Foster The People, Demi Lovato, Gym Class Heroes, LMFAO, Kelly Clarkson, David Guetta and Pitbull as well as surprise appearances from Karmin and The Script. LMFAO's Redfoo had to do a solo set alongside ShuffleBot and the band's dance crew, as bandmate/nephew Sky Blu was nursing a back injury. But that didn't prevent Red Foo from doffing his pants later for a smiley-face boxer version of the Speedo dance from the band's current No. 2 hit, "Sexy And I Know It."

Clarkson played a short, high-energy set that kicked off with 2004's "Since U Been Gone" and also included current single "What Doesn't Kill You (Stronger)," top 10 hit "Mr. Know It All" and a special duet of "Have Yourself A Merry Little Christmas" with Lovato. Guetta turned his set into a nonstop dance medley of his hits from current album "Nothing But The Beat," ranging from "Where Them Girls At" to Nicki Minaj's "Turn Me On" to the Sia-assisted "Titanium" to the top 10 Usher duet "Without You." "We have 15 minutes to turn this into the best dance party," he cheered from his oversized, heavily illuminated DJ booth.

Pitbull took a similar approach to his set, cramming in his raps from virtually every major single he's guested on during the last two years. He kicked off with his own "Hey Baby," teased a riff from Lenny Kravitz's "Are You Gonna Go My Way" and a snippet from Martin Solveig's "Hello," then played snippets from "Shut It Down "Rain Over Me," "International Love," "I Know You Want Me," Jennifer Lopez's "on the Floor," Enrique Iglesias' "I Like It" and Usher's "DJ Got Us Fallin' In Love Again." Last but not least was "Give Me Everything," the mega-hit that just became Billboard's No. 1 Radio Song of 2011.

"This was the first record that turned my life from a negative to a positive," the Miami rapper told the crowd. "This went number one all around the world thanks to you guys. Without Pitbull there is no love, and without love there is no movement."