Years ago when Taylor Swift's career was on the rise, the singer told Ellen DeGeneres that her celebrity crush was Justin Timberlake, while the two eventually met, the 25-year-old singer has now added singing alongside her idol to her bucket list.

On Aug. 26, the singer surprised the Los Angeles Staples Center crowd with a duet of "Mirrors" alongside Timberlake, reported Time.

"Justin hasn't performed since he became a dad, so I'm just honored that this is his first performance," Swift announced to a screaming crowd.

The singer, who welcomed his first son, Silas Randall Timberlake, with wife and actress Jessica Biel, shared a picture on Instagram of him and Swift goofing off backstage before they went on stage to perform.

While Timberlake, one of music's biggest stars, was enough of a surprise the night also included a performance by Selena Gomez who Swift joined in singing "Good For You" with.

The two singers, who are close friends, matched their looks on stage in shorts and over-knee-boots as they sang and danced to the soft tune, which Swift called the "song of the summer."

"After nearly 8 years of friendship, I just can't wait to tell our kids we ACTUALLY got to perform in front of thousands of insanely beautiful people together. TWICE! I love you Tay," Gomez captioned an image of the two on Instagram.

Swift posted her own image of her and Gomez and captioned it with, "Sisterhood. #1989TourLA."

Sisterhood. @selenagomez #1989TourLA A photo posted by Taylor Swift (@taylorswift) on Aug 27, 2015 at 1:51am PDT

According to Variety, fans were also treated to a performance of the song "Smelly Cat." The song was made famous by Lisa Kudrow, who played Phoebe Buffay on the hit television sitcom "Friends," and who Swift is a big fan of.

"She's only ever played in coffee houses before. She's never played in a big venue like this," Swift teased fans before bringing out Kudrow.

"The Rob Ellis Show" captured a video of Kudrow and Swift performing and posted it on Twitter.

Swift's shows at the Staples Center have also included appearances by Kobe Bryant, Beck, St. Vincent, Mary J. Blige, Chris Rock, Matt LeBlanc, John Legend and Alanis Morissette.