AceShowbiz -

The star-studded KIIS FM's 2017 iHeartRadio Jingle Ball was extra special with a surprise duet during Taylor Swift's set. The "Look What You Made Me Do" hitmaker reunited onstage with her best pal Ed Sheeran to close out the concert with her new song "End Game".

Wearing a loose-fitting sequined snakeskin-print shirt over black shorts, the country-turned-pop superstar also performed her older hits "Blank Space" and "Shake It Off", before delivering an acoustic, folksy rendition of "I Don't Want to Live Forever", which she recorded with Zayn Malik for BDSM movie "Fifty Shades Darker".

Earlier that night, Ed opened the show with acoustic versions of his own songs "Thinking Out Loud" and "Shape of You". Demi Lovato performed "No Promises" with Cheat Codes and brought out a gospel choir for her songs "Tell Me You Love Me" and "Sorry Not Sorry".

Lauren Jauregui of Fifth Harmony and Halsey teamed up for a performance of their collaboration "Strangers". Halsey later joined The Chainsmokers to sing "Closer". Kesha (previously known as Ke$ha) brought out Macklemore for their song "Good Old Days". She also performed "Woman" and "Praying".

Other performers at the concert included Charlie Puth, who performed "Attention", "See You Again" and Christmas classic "This Is Christmas", and Rapper Logic, who mixed holiday standard "Deck the Halls" with his with hit "Fade Away".

There was also a mini One Direction reunion, as Niall Horan and Liam Payne met backstage at the event. Other celebrities like Ryan Seacrest, comedian and late-night talk show host James Corden, Sarah Hyland, Lance Bass, Nicole Richie, Bella Thorne and Patrick Schwarzenegger mingled in both the building's VIP Forum Club and backstage.

A day later, on Saturday, Taylor Swift once again teamed up with Ed Sheeran at the 99.7 NOW's Poptopia concert at the SAP Center in San Jose, California. She showed her new style in a loose-fitting, long sleeve red, black and white plaid shirt over a mesh top, black shorts, paired with black lace-up boots.