IF YOU ASK Ivana Müller, audiences sitting still in the dark are the weirdest thing about theater. Hence, much of the Croatian artist's work is designed to flip that script on its ear. At TBA, she'll stage We Are Still Watching, "a show performed by its audience" that premiered last November in Amsterdam—but this is hardly the first time she's upended the traditional concept of performative roles.

Müller's While We Were Holding It Together, for instance, asks five performers to hold perfectly still for a 70-minute tableau vivant ("Not possible," she admits, because eventually "the body begins to move involuntarily..."). While physically frozen, they verbally propose scenarios for their characters: "I imagine we are in a museum," begins one, luring the others into a round of speculative description about gallery space and politics: They're part of a gallery's permanent collection—no, they're in storage, about to be sold off piecemeal. They've been discovered in a third-world country and commandeered for the British Museum—no, it's the Louvre.

Müller admits that her work can be absurd, humorous, and even subtly political, but her greatest fascination seems to be with articulating unspoken social contracts and ensemble efforts. In 2008's Playing Ensemble Again and Again, a chorus line moves toward their closing bow in slow-mo synchrony, confessing details about their own personal preparation ("I had to dye my hair black... I had to correct my speech impediment") and their relationships to their costars ("Some of us were friends and some of us were enemies").

Maybe it's no wonder that Müller is billed as a choreographer, performance artist, installation artist, text maker, video lecturer, audio producer, guided tour giver, and web creator—everything but a playwright. She seems determined to outsmart the theater art form—and if you think about it (as she forces you to), you'll see that she has a point. Assuming performers aren't who they say they are anyway, why limit them to one prescribed role? And why limit the privilege of performing to actors, when the audience is equally engaged in the story? Once we acknowledge character as a pose, why even put players through all the motions? Why not try fewer gestures and more conjecture, and see what happens?

We Are Still Watching will take one more slow-motion step into the audience's comfort zone, enveloping would-be spectators in the ensemble energy that's more often confined to the stage. So good luck trying to sit still in the dark.