[PHOTO] Taylor Swift Surprises Fans: Selena Gomez Joins ‘Bad Blood’ Singer On Stage In A ‘Good For You’ Duet

Taylor Swift astounded her fans as well as Selena Gomez's after the latter suddenly appeared on stage the final leg of her"1989" tour.

Fans of Taylor Swift were surprised when Selena Gomez emerged on stage singing "Good For You" during Swift's fifth and last 1989 World Tour concert at the Staples Center in Los Angeles last Aug. 26.

Though news have been taking rounds since Aug. 17 that Taylor Swift is bringing Selena Gomez on stage in one of her concerts (being BFFs and all) is joining her concert, no one really knows when exactly it will happen -until T-Swizzle's Los Angeles concert.

Taylor Swift and Selena Gomez both rocked the stage in an astonishing final both wearing a matching black-and-white shorts and over-the-knee boots - and of course, fans of both singers were ecstatic!

"@taylorswift13 @selenagomez What just happened?!?? #GoodForYou #1989TourLA," Twitter user @jennifer2525 wrote. Hollywood Life reported that Taylor Swift also filled her concert with other stunning stars such as Gigi Hadid, Nick Jonas Julia Roberts and Lena Dunham for a rendition of the "F.R.I.E.N.D.S. favorite, "Smelly Cat," before closing down the show with Justin Timberlake," said Hollywoodlife.

Swift also delighted every "F.R.I.E.N.D.S." fans in the audience with a rendition of Phoebe Buffay's "Smelly Cat" in a duet with no other than Lisa Kudrow herself. In June, Swift said that singing with Gomez was"a favorite thing she's ever done."

Indeed, the friendship of Taylor Swift and Selena Gomez has gone a long way, not only on stage but also off stage.

"I can count in one hand the people I could call and who would be there for me.Taylor is one of the greatest people," Selena toldUK's Sunday Times

"When I split with my first boyfriend and I was really sad about it, she flew into town with homemade cookies and a bunch of junk food," Gomez recounted. "To this day, if I called her, she would do the same thing, despite being one of the busiest people in the world,"

Taylor will also rock the stage in Shanghai, Singapore and Australia next month.