Christina Aguilera & Lil’ Kim Reunite for ‘Lady Marmalade’ at Concert Attended by the Clintons

Christina Aguilera kicked off the New York City dates of her highly anticipated Liberation Tour with a bang

Dave Quinn is a Senior Editor for PEOPLE. He has been working at the brand since 2016, and is the author of the No. 1 New York Times best-selling book, Not All Diamonds and Rosé: The Inside Story of the Real Housewives from the People Who Lived It.

PHOTO: KEVIN MAZUR/GETTY

Christina Aguilera kicked off the New York City dates of her highly anticipated Liberation Tour with a bang on Wednesday

The powerhouse singer, 37, surprised the sold-out crowd at Radio City Music Hall with a very special guest: rapper Lil’ Kim.

Both musicians have a history together, having collaborated back in 2001 on the Moulin Rouge soundtrack hit “Lady Marmalade” (alongside Mya and Pink) and again in 2002 on Aguilera’s Strippedtrack “Can’t Hold Us Down.” The LaBelle cover won them the Grammy for best pop collaboration with vocals.

Aguilera was in the midst of singing the song when she brought Lil’ Kim out, telling the crowd on Wednesday, “We got a surprise — Lil’ Kim, Lil’ Kim, Lil’ Kim!”

The rapper, 44, then appeared on stage decked out in a sparkling grey bodysuit with sheer panels, spitting her iconic “Lady Marmalade” rhymes once again.

Among the folks watching from the audience was former President Bill Clinton and Hillary Clinton, who got cheers of their own when they arrived at the famed venue. Later, they posed with Aguilera backstage. Bill, 72, and Hillary, 70, wore classic pants and blazers as Aguilera rocked a corseted red ruffle gown.

 Christina Aguilera Feels ‘Fulfilled and Alive’ After First Tour Stop in 10 Years

KEVIN MAZUR/GETTY

Bill Clinton, Christina Aguilera and Hillary Clinton

That gown is one of the many looks Aguilera wears during her Liberation Tour.

Other looks — from designers like Milligan Beaumont, Gareth Pugh and Joshua Kim — include a high-shouldered sequin gown, an oversized jacket, and a black and red leather ensemble with chaps, straight from her “Dirrty” video.

There’s also a dramatic wedding-inspired white tulle gown that she wears while singing the ballad “Unless It’s with You.” Afterwards, Aguilera helped facilitate a marriage proposal onstage. She started a similar tradition late last month when her tour kicked off at the Hard Rock Live in Hollywood, Florida.

 WATCH: Christina Aguilera Gives Fans a Peek at Her First Tour in More Than a Decade

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Christina Aguilera

KEVIN MAZUR/GETTY

Christina Aguilera

KEVIN MAZUR/GETTY

Christina Aguilera stands by as a couple gets engaged at her tour stop

This is Aguilera’s first tour in a decade. Her setlist includes many songs from her new album Liberation, including “Fall in Line,” “Maria” and “Accelerate” — as well as old favorites like “Fighter,” “Beautiful,” “Ain’t No Other Man,” “Genie in a Bottle,” “Can’t Hold Us Down,” “What a Girl Wants” and “Come on Over (All I Want Is You).”

“What an amazing warm welcome back to the stage after 10 years (too many!),” Aguilera wrote on Instagram after her first show, captioning a gallery of photos from the tour. “[It] felt like coming HOME again!!”

“Thanks to all of you in Florida for your beautiful energy,” she added. “I feel fulfilled and alive and cannot wait to see you Fighters in New Jersey on Friday. #LiberationTour.”

RELATED: Go Inside Christina Aguilera’s Liberation Tour

Liberation was Aguilera’s first new studio album since 2012’s Lotus.

Though she hasn’t put out a full LP since then, there have been singles. In 2013, she guested on Pitbull’s “Feel This Moment,” Mexican singer Alejandro Fernández’s cover of “Hoy Tengo Ganas de Ti,” and A Great Big World‘s “Say Something.” That same year, she recorded “We Remain” for The Hunger Games: Catching Fire soundtrack.

She appeared on a remixed version of Lady Gaga‘s 2014 single “Do What U Want.”

In June 2016, Aguilera released “Change” — a song dedicated to the late Christina Grimmie and the victims of the Orlando nightclub shooting. Two months later, she dropped a disco song called “Telepathy” for the soundtrack of Netflix’s The Get Down.

 Christina Aguilera Poses with Daughter Summer Ahead of Her Liberation Tour: ‘Roadie 4 Life’

Of course, in her time away from music, Aguilera has remained busy in her personal life. In 2014, she got engaged to fiancé Matthew Rutler. The couple are parents to 4-year-old daughter Summer Rain. Aguilera also has a 10-year-old son Max Liron from her first marriage to ex Jordan Bratman.