Christina Aguilera, Jimmy Fallon perform in disguise on 'Tonight Show'

June 15 (UPI) -- Christina Aguilera and Jimmy Fallon donned disguises to perform inside a New York City subway station on The Tonight Show.

Aguilera and Fallon went undercover Thursday by wearing wigs, hats and sunglasses before taking the stage to perform Aretha Franklin's "Think."

The singer and late night host then took off their costumes and surprised the large cheering crowd that had formed before performing Aguilera's classic 2002 single, "Fighter."

The subway concert included the live audience singing along the lyrics to "Fighter" and Fallon interacting with the crowd as Aguilera rocked the microphone.

Aguilera's eight studio album Liberation, is now available. The project includes a duet between Aguilera and Demi Lovato titled "Fall in Line." The duo recently released a music video for the song.

Aguilera is also set to embark on a North American tour that begins Sept. 25 at Hard Rock Live in Hollywood, Fla., before wrapping up Nov. 13 at the Mahaffey Theatre in St. Petersburg, Fla. She will also be performing in cities such as New York, Chicago, Boston, Denver, Los Angeles and Las Vegas.