Katy Perry performs at the night that changed America: a Grammy salute to the Beatles, on Monday, Jan. 27, 2014, in Los Angeles. (Photo by Zach Cordner/Invision/AP)
Katy Perry performs "Dark Horse" at the 56th annual Grammy Awards at Staples Center on Sunday, Jan. 26, 2014, in Los Angeles. (Photo by Matt Sayles/Invision/AP)
Katy Perry performs "Dark Horse" at the 56th annual Grammy Awards at Staples Center on Sunday, Jan. 26, 2014, in Los Angeles. (Photo by Matt Sayles/Invision/AP)
Katy Perry performs "Dark Horse" at the 56th annual Grammy Awards at Staples Center on Sunday, Jan. 26, 2014, in Los Angeles. (Photo by Matt Sayles/Invision/AP)
Katy Perry performs "Dark Horse" at the 56th annual Grammy Awards at Staples Center on Sunday, Jan. 26, 2014, in Los Angeles. (Photo by Matt Sayles/Invision/AP)