Taylor Swift, Sabrina Carpenter Serve Surprise Mix of ‘Espresso,' ‘Is It Over Now?' & ‘Please Please Please' in New Orleans

Taylor Swift served "Espresso" and more with with Sabrina Carpenter in New Orleans Saturday night (Oct. 26).

Swift teased she was about to do something different for her acoustic set during her latest stop on The Eras Tour - sing someone else's song. "It's been stuck in my head," she explained to the crowd at Caesars Superdome of her choice to bring a new flavor to the surprise song menu.

To the delight of many, she launched into Carpenter's massive summer hit "Espresso" on her guitar. Then she paused and asked her fans a silly question - "Is it OK if I call her, and you guys can say hi?" - and picked up a cell phone to get Sabrina on the line.

The pair of pop stars acted out a bit, with Swift putting Carpenter on speakerphone, holding it up to the mic and asking her how long it might take her to get to the stadium.

As it turns out, about five seconds later they were on stage together, working "Espresso" into a three-song mashup with Swift's 1989 vault track "Is It Over Now?" and another one of Carpenter's big hits, "Please Please Please."

The highlight of Swift's Saturday night? Having an excuse to sing the "Espresso" lyric "I'm working late ‘cause I'm a singer" to a sold-out stadium as it neared 11 p.m. at night.

"She has literally one day off. She is on tour. This is crazy that she came to perform for us," Swift said at the end of their crowd-pleasing duet. Carpenter exited the stage, leaving Swift to wrap the evening's acoustic section on her own at the piano, where she played a mashup of Midnights bonus song "Hits Different" and 1989 opener "Welcome to New York."

Watch clips of their surprise performance below.