The singer sang "Let It Go" with the Frozen star at her concert in Tampa, Fla. on Halloween...in costume!
Taylor Swift surprised her sold-out Atlanta crowd with the "Talking Body" crooner.
Blake Shelton's ex-wife joined Swift onstage to perform "Little Red Wagon."
With just a few U.S. dates to go, Swift continued to surprise fans with an impromptu performance of "Love Me Like You Do" in Texas.
The "Boom Clap" crooner joined her friend on stage for another electrifying performance in front of 50,000 fans.
Goin' country in Toronto! Swift brought out the American Idol judge.
During the St. Louis show, T.Swift and the hometown rapper had a blast singing his greatest hits.
Swift proved she had moves like Jagger when she brought the Rolling Stones frontman on stage in Nashville to sing "Satisfaction."
Swift and the Aerosmith frontman sang his band's 1998 hit "I Don't Want to Miss a Thing."
At a concert in Nashville, Swift sang "When You Say Nothing At All" with the country star, who released a cover of the ballad in 1995.
Swift and the country singer performed Ballerini's 2014 hit "Love Me Like You Mean It" in Nashville.
The group performed "If I Die Young" at Bankers Life Fieldhouse in Indianapolis.
The two performed at the Minute Maid Park in Houston.
The singer performed "Complicated" with the Canadian pop star at her concert in San Diego.
The singer brought her "Bad Blood" co-star and bestie on stage for her final Los Angeles show.
At her final L.A. show, Swift asked the new dad to perform for the first time since baby Silas' birth.
We're so jealous! Swift got to sing one of the most iconic breakup songs of all time ("You Oughta Know") with the person who wrote it.
For one of her five sold-out Los Angeles shows, Taylor got some indie cred by having Beck and St. Vincent perform "Dreams" with her.
The Emmy-winning talk-show host showed up in a sparkly tutu ensemble that rivaled Swift's.
The besties performed a duet to "Royals" in Washington D.C.
Swift proved she rolled deep by having her squad join her during her New Jersey show.
At her Seattle show, Swift invited the rapper to sing his hit "Trap Queen" with her. She later shared an Instagram pic of the moment and claimed she was "unable to find my chill."
Taylor's cameos for her London leg were a real model squad.
The World Cup-winning soccer team waved American flags while walking the catwalk during one of Swift's New Jersey stops.