Nick Jonas surprised everybody when he appeared at the Taylor Swift concert Saturday night in East Rutherford, New Jersey. Jonas teamed up with Swift to perform the song, “Jealous,” and the audience went wild.

"Unreal feeling jumping on stage with my friend @TaylorSwift13 tonight at the #1989TourEastRutherford show in my hometown," Jonas wrote on Twitter. "Thank you so much @TaylorSwift13 for having me. What an incredible memory…"

The duo last got together six years ago for a concert and Swift reminisced about that time on Twitter by sharing an old picture and juxtaposing it with a picture from Saturday night’s concert at MetLife Stadium. “I feel all the feelings now,” Swift captioned the image that shows her with longer, curlier hair. Jonas looks the same, sans his abs. “Oh wow. Time flies when you’re having fun ha,” the singer replied to Swift on Twitter.

“Nick let Taylor take the reins in the song. It was such an amazing moment,” Hollywood Life wrote, describing the moment. “The crowd went wild for the duet, cheering and waving their hands along to the beat. Taylor and Nick danced together up on stage, and fans love it,” the website added. Swift and Jonas are longtime BFFs, and the songstress also dated Jonas' older brother Joe Jonas in 2007.

Swift loves surprising her fans during her concerts. The “Bad Blood” singer Friday roped in the Weeknd for a performance of his summer hit "Can't Feel My Face" and also bought the reigning world champion U.S. Women's Soccer Team on the stage of her “1989 World Tour.”

Her previous stage guests include Gigi Hadid, Martha Hunt, Lily Aldridge and Karlie Kloss. She has also invited reigning world champion tennis player Serena Williams. In the past, Swift introduced Adam Levine's wife, model Behati Prinsloo, and model Candice Swanepoel during one of her recent concerts. “Orange is the New Black” actress Uzo Aduba was also invited on stage as a special guest for performing on "Style.” See Nick Jonas-Taylor Swift video below: