Fans went crazy when Lil Kim joined Christina Aguilera on stage during her show at Radio City Music Hall to perform "Lady Marmalade."
A Great Big World also came out to help Christina perform "Say Something," but the real treat was Kim hitting the stage for the cover they did back in 2001 for the movie "Moulin Rouge."
Even though Mya and Pink weren't there to aid in the performance fans still loved it!
Bill and Hillary Clinton were also in attendance for the show and looked like they were having a great time.
Check out a snippet of their performance below: