Taylor Swift's neverending stream of star guests on her current 1989 World Tour has at times left us worried that she might actually run out of celeb pals to join her on stage.

However the ever-resourceful pop princess yesterday pulled a big one out of the bag when not only was she joined by girl group Fifth Harmony, but she then joined THEM for a rendition of their hit Worth It.

Oh, and did we mention that she even wore a matching outfit? We think we're going to call them "Swift Harmony".

Sharing a snap of them all together in their blue dresses, she wrote: "So stoked this pic exists because this was SO MUCH FUN @FifthHarmony"

And she also shared a pre-show group photo at the gig venue in Santa Clara, California, which she captioned: "Sound check with @fifthharmony right after they taught me their choreo and before they lent me one of their outfits so we could all be twinzies."

Tay-Tay has been joined by a host of stars on her tour previously, including Lorde, Cara Delevingne, Gigi Hadid, Nick Jonas, Kendall Jenner and Walk The Moon.