The Rolling Stones, who are currently on their 50 and Counting tour, surprised concert-goers when they brought “Part of Me” singer Katy Perry up on stage to sing a song with them over the weekend.

At their Las Vegas stop on Saturday night, Perry joined Mick Jagger and crew at the MGM Grand Garden Arena on the Some Girls track "Beast of Burden."

Rolling Stone reports Perry and Jagger got together for a duet, which the Stones announced would happen on Twitter earlier that day.

They wrote:

Perry told them in reply, "I'm much obliged & quite honored!" Jagger also tweeted, “Hey guys, really looking forward to duetting with Katy tonight, Mick @katyperry #Stones50.”

After the show, Perry took to Twitter to joke “Yes, I just did gyrated on Mick Jagger. WHAT?! #Stones50.”

Perry started her duet with Jagger about six songs into the concert. Other singers who have joined them on stage are Tom Waits, Gwen Stefani and more.

image: INF Daily