The Grammy-winning singer, 37, and comedian, 43, put on disguises and went undercover for the performance — which was filmed and aired on The Tonight Show Starring Jimmy Fallon.
Aguilera wore a brown wig, oversized hat, and dark shades for the look, covering herself in a big dress with a denim top and green skirt. Fallon, meanwhile, rocked a long wig, hat, and sunglasses of his own, but upped the ante with a fake goatee.
Of course, no amount of costuming could hide Aguilera’s voice. The songstress was immediately recognizable when she opened her mouth, belting a cover of Aretha Franklin’s 1968 soul classic “Think” (with Fallon on the banjo).
Crowds soon formed around the pair. By the song’s end, they were met with a sea of applause — perfect timing as Fallon was happy to finally reveal their true identities.
“We’d like to do one more song for you if you don’t mind right here,” Fallon said. “First we’d like to introduce ourselves, my name is Jimmy Fallon and this is Christina Aguilera. Welcome to New York City and welcome to the subway!”
“It’s so hot in here, oh my God,” Aguilera lamented.
The duo then sang a cover of Aguilera’s 2002 bop “Fighter.” Aguilera later appeared in studio on The Tonight Show and performed her latest single, “Fall in Line.”
This isn’t the first time Fallon has subway busked with top music talent. Aguilera’s Voice co-coach Adam Levine had previously participated in a similar segment with Fallon back in November, while another Voice alum — Miley Cyrus — kicked off the bit in January 2017.
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Aguilera’s Tonight Show appearance is part of the many press stops the singer has been doing in support for her latest album, Liberation.
Out now, the 13-track LP is Aguilera’s first album since 2012’s Lotus. Aguilera has long-promised fans that new music was coming, and finally came through back in May with the release of her first single, “Accelerate.”
“Fall in Line,” a duet with Demi Lovato, dropped days later before the two performed the female empowerment anthem together on the 2018 Billboard Music Awards.
This fall, she’ll embark on her first North American concert tour in 10 years. The 22-date Liberation Tour kicks off Sept. 25 in Hollywood, Florida — one month shy of the 10-year anniversary of Aguilera’s final Back to Basics Tour stop on Oct. 24, 2008.
The Tonight Show Starring Jimmy Fallon airs weeknights (11:30 p.m.) on NBC.