An all-female lineup kicked off the 2016 ACM Party for a Cause on Friday night (April 1), with Lauren Alaina, Kelsea Ballerini, Kelleigh Bannen, Cam, Brandy Clark, Jana Kramer, Maddie & Tae, Martina McBride and Kellie Pickler all taking the stage at the Las Vegas Festival Grounds before Carrie Underwood closed out the night. But the crowd also got a surprise guest: Miranda Lambert.

The two country superstars joined forces to sing their 2014 duet, "Somethin' Bad." Press play on the video above to watch a snippet of their performance. "Somethin' Bad," was nominated for two ACM Awards in 2015, for Vocal Event of the Year and Video of the Year.

In addition to Lambert's surprise appearance, Alaina, Bannen, Kramer and Pickler joined Underwood onstage for "Before He Cheats." During her set, Underwood also received the 2016 ACM Lifting Lives Gary Haber Award, which recognizes an artist or industry professional “who is committed to serving others, has a generosity of spirit and shows a dedication to helping those in need.” Underwood was one of the first country stars to partner with ACM Lifting Lives, the Academy of Country Music’s charitable arm, and is involved with, among others, Make-a-Wish, Operation Homefront and her own C.A.T.S. Foundation.

Both Underwood and Lambert are nominated for Female Vocalist of the Year at this year's ACM Awards. Additionally, Lambert is up for Entertainer of the Year and Vocal Event of the Year.

The 2016 ACM Awards are set to air live from the MGM Grand Garden Arena in Las Vegas, Nev., on Sunday night (April 3). The ceremony will begin at 8PM ET on CBS. The 2016 ACM Party for a Cause wraps up on Sunday night as well.

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