Billie Eilish surprised her audience when she brought out Hayley Williams during the Coachella Valley Music And Arts Festival in Indio, California, on Saturday.

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The star - born Billie Eilish Pirate Baird O'Connell - paired her casual look with a couple of layered chunky necklaces.

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Meanwhile Williams looked cool as ever in a well-fitted black blazer that gave a peek at her trim midsection, and matching black pants.

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The Mississippi born beauty wore her auburn tresses in a free-flowing style, rocking bangs that framed her face.

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Billie also sported black knee-pads on her knees, which came in handy as TMZ reported that she took a tumble during her performance.

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[{"selector":"#anim-d37c7983-a24d-47cb-9515-b03d790360f9 [data-leaf-element=\"true\"]","keyframes":{"transform":["translate3d(-11.556100449317764%, 0, 0)","translate3d(0%, 0, 0)"]},"delay":0,"duration":4000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"both"}] [{"selector":"#anim-5a0b01a4-5d44-47d6-8a1b-c2a80acee0e2","keyframes":{"opacity":[0,1]},"delay":0,"duration":4000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"both"}] [{"selector":"#anim-95558ecf-f08d-4694-bfdb-2d6d4922edc2","keyframes":{"transform":["scale(0.3333333333333333)","scale(1)"]},"delay":0,"duration":4000,"easing":"cubic-bezier(.3,0,.55,1)","fill":"forwards"}] Billie Eilish, one of the major headliners this year, chose to share her stage with some special guests on Weekend 1 and her second appearance on Saturday, April 23 was just as impressive.