This is certainly not a new couple alert in the Biblical sense, but shock rocker Alice Cooper and pop tart Ke$ha have a "thing" that they like to do in public and that's hit the stage together.

Cooper joined the 'Tik Tok' singer on stage in Oslo, Norway last night to perform his hard rock standard 'School's Out' together. The singers previously appeared on stage together in October of last year, when Ke$ha showed up at Cooper's Nashville, Tenn. show, as it's her hometown. Apparently, Cooper was already in Norway for his own show, slated for tonight. The Rock and Roll Hall of Fame inductee stopped by her soundcheck and that's when the idea to perform together than night was born.

The Coop has gotten into the habit of hopping on stage with artists outside of his genre. He performed a medley of songs with the Foo Fighters on Saturday, July 2nd, at that band's gig in Milton Keynes, England. Even stranger, during his own gig in London in June, Cooper brought Johnny Depp on stage to play guitar with him.

Watch Alice Cooper and Ke$ha perform 'School's Out'

Ke$ha posted a Tweet after the fact, writing: "Thanx for coming to Oslo to do 'SCHOOLS OUT' with me dad... LEGEND. F**KING LEGEND." Cooper was quick to reply, tweeting: "Thanks keshasuxx! Next time our stage, and be sure to bring some bandaids (sic)."

We're looking forward to the third installment of the Alice Cooper/Ke$ha live collaboration.