Down with the crowd: Katy Perry showed her fans a little more than they bargained for as she took to the stage at the Hollywood BowlKn-ellie-ng: Miss Goulding was quite literally singing from her toes at the charity concertStanding straight: Ellie and Katy during a meet-and-great for a radio station before the concert beganSilver bird: Katy went for a bright choice of outfit wearing a silver jacket over a skirt and top-combo in the same material, paired with knee-high socksHow high? There was no mistaking Miss Perry’s energy on stage at the Hollywood BowlStrictly retro: Katy completed her 90s inspired outfit with a ponytail on top of her headListen up: Resembling a futuristic schoolgirl, Katy Perry took in everything her support had to sayJump around: You could certainly hear Katy Perry ‘Roar’ as she took over the stage on Wednesday nightPride of Britain: Ellie was not one to be outdone by Miss Perry, as she belted out her finest hitsGirl power: Ellie and Katy were joined on stage by Bonnie McKee, Sara Bareilles, Tegan and Sara, and Kacey Musgraves to sing her hit RoarKaty fan: Jessica Alba attended the show dressed in a train conductor style hat and a yellow sweaterBFF: Katy Perry’s best friend Bonnie McKee, who co-wrote many of her biggest hist include Roar and California Girls, also sang for charitySweet tones: Country star Kacey Musgraves performed songs form her third album Same Trailer, Different Park