Christina Aguilera and Jimmy Fallon surprise fans with a performance at the NYC subway. The two celebrities disguised themselves while busking right below the Rockefeller Center in the Big Apple.

NYC Subway Busking

The over three-minute clip was shown during this week's episode of The Tonight Show Starring Jimmy Fallon. Aguilera performed two songs. Their first track is a cover of Aretha Franklin's hit single "Think." The performance took place while Aguilera and Fallon were wearing wigs, hats, and sunglasses.

After singing just a few words, subway goers already had a hint that it was Aguilera singing. After all, the singer's signature low and raspy voice is quite unique. Fans started piling up close to Aguilera and Fallon, and they also recorded the duo's performance.

Christina Aguilera Performs 'Fighter'

Before singing Aguilera's hit song, "Fighter," Fallon removed their disguises and introduced themselves. The crowds broke into loud cheers and applause. While singing "Fighter," Fallon hilariously ran around while playing a fake instrument.

Fallon did not sing "Fighter" with Aguilera. Instead, he encouraged the audience to cheer for the singer.

'Liberation' Release

Aguilera paid The Tonight Show Starring Jimmy Fallon a visit to promote her new album Liberation, which was released on the same day. During her conversation with Fallon, the talk show host congratulated Aguilera on her latest venture.

Fallon also asked Aguilera why she decided to call her album Liberation. She said that she felt it is time to be true to herself and be secure in her own voice. The singer also wants to inspire more people to do the same.

The songs featured in Liberation are "Liberation," "Searching for Maria," "Sick of Sittin'," "Dreamers" (feat. Summer Rain), "Fall In Line" (feat. Demi Lovato), "Right Moves" (feat. Keida & Sheseea), "Like I Do" (feat. Goldlink), "Deserve," "Twice," "I Don't Need It Anymore," "Accelerate" (feat. 2 Chainz & Ty Dolla $ign), "Pipe" (feat. XNDA), "Masochist," and "Unless It's You."

'PJ Masks' Theme Song

Aguilera also revealed that her daughter's voice is on her album, particularly in the song "Dreamers." The singer said that Summer Rain listens to her whenever she does her vocal exercises. The young girl is also obsessed with "Peppa Pig," "PJ Masks," and "Paw Patrol."

Among all three cartoons, Summer Rain is most obsessed with "PJ Masks." Aguilera managed to memorize the lyrics of the show's theme song because her daughter always wants her to sing it. Fallon revealed that he is also familiar to the song because his children watch it at home.