Dancing With The Stars wrapped up its 20th (!) season last night, and Sia joined the celebration to sing her 1000 Forms Of Fear single “Elastic Heart.” Judge Julianne Hough and her brother, Derek, took part in an elaborately choreographed performance that pits two adults and the child versions of themselves against each other, and lets their fights play out in parallel. All of the dancers carry on the jerky movement that Maddie Ziegler adopted for her trilogy of videos. Sia looms in a window-frame in the background, her wig covering her face as usual. Watch below.