Taylor Swift took to the Staples Center stage on Thursday night and sang a number of her hit singles. That would have been enough for the thousands of fans in attendance, of course. But the crowd - and Taylor herself - got a surprise when Katy Perry popped out and sung "Hot N' Cold" with the young Grammy Award-winner. Check out the duet below: A Perry Cool Surprise Swift will release a new album this fall. We can't wait for it. As the anticipation builds, check out the following photos of Taylor performing in Los Angeles: