Rapper B.o.B. joined Taylor Swift on stage to sing his hit song 'Airplanes' at her Speak Now Dallas show on October 8. On Saturday night, Swift backed up the hip-hop star, singing pop-star Hayley Williams' part. Williams sings with B.o.B. in the original version.

“Had a night to remember in Dallas performing one of my biggest songs with the ever-so enchanting Taylor Swift,” B.o.B. tweeted.

It's the second time in less than a week Swift has stood back to let someone from outside of country music shine on her stage. In Atlanta on Oct. 2, rapper T.I. performed 'Live Your Life' while Swift sang Rihanna's part. Hip-hop famers Nicki Minaj and Usher have also been unexpected collaborators on the Speak Now tour.

After the Dallas show, Swift gushed about how much fun she had on Twitter, saying, "Tonight was like a dream. That crowd.. The biggest indoor stadium in the world. And singing ‘Airplanes’ with B.O.B. !!!!!"

Tim McGraw, Kenny Chesney and Ronnie Dunn have also made cameo appearances on the Swift tour in recent weeks, and Swift has interrupted her set to sing cover songs by Sugarland, Britney Spears, Alan Jackson and Brooks and Dunn.

Watch Taylor Swift Perform With B.o.B.