In what is perhaps the country's best improv city, this is perhaps the best ongoing improv show, long-form or otherwise. T.J. and Dave hasn't changed much since its debut in February 2002: same stage, time slot, and price, same opening Ike Reilly songs and introductory caveat, "Trust us, this is all made up." There's still no director or show description. Yet the show about nothing has a healthy cult following. T.J. Jagodowski and Dave Pasquesi, who have 30 years of stage time between them, are what most improvisers are not (liberally intelligent, extremely talented actors as well as comedians) and do what most improvisers do not (carefully listen to each other before responding). The result is an exhibition of verbal facility and pantomimic agility--they can do everything from multiple English accents to magic tricks--that anticipates and plays off the audience's reactions. During their hour of subtle character development, it's easy to forget it's all made up. Open run: Wed 11 PM, I.O., 3541 N. Clark, 773-880-0199, $5.