Glitterball, at Cafe Voltaire.
For some reason--perhaps a lack of natural predators or too many growth hormones in our beef--the population of long-form improvisers has exploded in recent years. It seems every available back room, late-night space, and coffee shop basement is infested with them. And in many ways, Glitterball is just one more troupe. Like everyone else, Glitterball creates a full-length, two-act play out of thin air. Like everyone else, they define a "full-length play" very loosely--what they call a two-act "improv extravaganza" is really a shapeless series of scenes that don't build to a climax or end with any resolution.
Unlike 90 percent of the improvisers in Chicago, however, the three actors who make up Glitterball--Peter Gwinn, Laura Krafft, and Edmund O'Brien--have a definite gift for creating vivid, original characters who are (gasp!) interesting to watch. O'Brien, for example, managed to conjure up an aggressive, annoying eccentric who (1) actually resembled eccentrics I have known, (2) never got on the audience's nerves, and (3) was funny and charming, in a twisted way. Similarly, Krafft managed--thanks in part to her sensitive male collaborators--to create a host of characters, none of whom was a girlfriend, a wife, or a secretary.
Now if Glitterball could just figure out how to create a coherent plot.