Miguel and AlunaGeorge alone are enough to set this show apart from the sprouting graveyard of Halloween-week events vying for your attention. Adding Sia — and 14-year-old Dance Moms wunderkind Maddie Ziegler, her snarling spirit-animal avatar in some of the most effective and affecting pop videos of this century — pushes it into the realm of the hottest tickets of the year. Sia hasn't toured since 2011, which is to say before she became Sia, the mononymous, wigged-out superstar who broke YouTube in 2014 with the cagey representation of herself as a 4-foot beehive of unbridled energy and impossible body control. Today, "Elastic Heart" (with Ziegler taunting a transformational Shia LaBeouf in a prison ballet) and "Chandelier" (a possessed, solo hotel-room showstopper) together own enough views to have been seen by more than a quarter of everyone on Earth. At the 2015 Grammy Awards, Sia enlisted a second platinum stand-in: Kristen Wiig, who writhed with Ziegler around a trashed-room set, in a trading-places, domestic-abuse mise en scene, as the singer/songwriter performed "Chandelier" while facing the back wall, never once turning around. This "Nostalgic for the Present" production also backgrounds her, with videotaped cameos dancing in step with Ziegler's onstage movements. Like everything else Sia does, it's anything but routine. Tickets $32-$122 plus fees.