It was a weekend of surprises for Taylor Swift's Philadelphia concert goers.
Taylor and Rachel Platten enjoyed singing "Fight Song" together backstage so much last week, they decided to perform it in front of 50,000 at Swift's Philadelphia show on Saturday. The two walked side-by-side to sing Platten's rising Billboard Hot 100 song (it currently sits at No. 25) before giving each other a hug to finish out their single-song performance.
Platten, who's joining Colbie Caillat and Christina Perri on tour later this summer, wasn't the only special guest Tay Tay had in Philly. At Friday night's show, the "Bad Blood" singer brought out Echosmith to perform their hit "Cool Kids" together, then Mariska Hargitay during her performance of "Style."