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:
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: