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 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 Stripped track “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.