Selena Gomez may be in the middle of her own “We Own The Night” tour, but that didn’t stop her from making a special appearance at best friend’s own concert.

The 19-year-old half-Mexican singer/actress joined Taylor Swift on stage at her sold-out show at New York City’s Madison Square Garden—the last stop on the country superstar’s worldwide “Speak Now” tour.

Swift invited Gomez to perform their first-ever duet together. While the crowd went absolutely wild, Swift and her “best friend” Gomez, performed a live rendition of Gomez’s hit “Who Says?”

When Gomez returned to the stage sometime later for a final bow, she’d changed out of her sparkly black mini-dress and was wearing a Taylor Swift tour t-shirt!