Katy Perry Joins Taylor Swift On Stage During LA Concert

Katy Perry surprised fans at Taylor Swift's sold out LA concert at the Staples Center last night. The two sang a duet of Perry's hit "Hot N Cold." Swift tweeted later that night: "Surprise guest at Staples Center: @katyperry!! We sang Hot N Cold and jumped up and down a lot. Katy! LA! I will always love you!"