It's rare to see a Britney Spears song performed "live" by the singer herself -- but last night, Kelly Clarkson gave it a try!

Throughout her tour, the original "American Idol" champ has been playing covers of other people's songs during her shows -- and at Tuesday night's L.A. stop of her Stronger tour, she decided to cover Britney's "Till the World Ends."

"I thought this would be a fun one you might enjoy," she said before singing. "I know you know this song, I'm expecting everybody on these Os!"

She killed it, telling the crowd after "I love that song. I always get this bad taste in my mouth though when I hear Britney Spears because usually she's my cardio music and I frickin hate cardio! I frickin' hate the gym ... the gym can suck it!"

During Kelly's L.A. show she also had a parade of special guests including Reba McEntire, Michelle Branch, Blake Shelton and fellow "Idol" alum Tamyra Gray.

The crowd went wild when Blake walked out to perform "Don't You Wanna Stay" with Kelly:

Kelly and Tamyra also impressed by covering Whitney Houston and Mariah Carey's "When You Believe":

Ladies can saaaaang!

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