Miley Cyrus, Madonna Grind on Stage During "Don't Tell Me," "We Can't Stop" Medley on MTV Unplugged

BFFs who can't stop! Madonna lent her vocal talents -- and body -- to Miley Cyrus' MTV Unplugged concert special, which aired Wednesday, Jan. 29. The 55-year-old Material Girl performed a duet medley of her Western-themed 2000 hit "Don't Tell Me" and Cyrus' 2013 party anthem "We Can't Stop."

The 21-year-old former Disney star kicked off the performance solo before Madonna popped up in the audience and joined her on stage. The ladies, wearing sexy cowgirl outfits, quickly started grinding and dirty dancing together with Cyrus even spanking Madonna's butt. For the grand finale, the pop stars broke out into the synchronized country dancing routine from "Don't Tell Me."

"That was pretty f----ing cool, you guys," Cyrus told the audience after the duet. "It sounds super-lame, but as a pop star it's pretty cool performing with Madonna . . . Today was one of those days that it was really easy to get out of bed, put on a bikini and sing with Madonna."

Watch the video above and tell Us what you think of the performance!