Sia was the musical guest on last night's Jimmy Fallon, and the singer -- who will release her new album This Is Acting tomorrow -- was joined by Natalie Portman, the Roots, and Fallon to perform traditional New Orleans song "Iko Iko." She also did "Cheap Thrills" from her upcoming album. Watch both performances below.
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This Is Acting is out 1/29 via RCA.






