ImprovEverywhere organize theatric performances. Staged in completely public areas. So at any moment, in the street out in public, a performance might take place. This one, is on a subway; and it's a scene from Star Wars; and it's epic.
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Obviously, well planned (except when it turns out Vader is too tall to fit through the door and smacks his head!), with renting costumes, planning subway stops, and script timing. The looks on peoples faces watching the performance unfold is a joy, especially the kids. That and the number of cameras that get pulled out -- everyone has a camera. Of course, they do multiple performances over the course of a few hours, to get full use of all that planning.

Also check out Frozen in Grand Central. Excellent job guys!