The fourth edition of this annual celebration of the art of improvisational comedy brings together performers from around the U.S. and abroad. Current and former Chicagoans include members and alumni of the Second City, ComedySportz, the Upright Citizens Brigade, Schadenfreude, Annoyance Productions, and ImprovOlympic. In addition to the performances there’ll be discussions, forums, workshops, and a minifestival of improvised “movies.”

Slotnick Katz & Lehr

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Joey Slotnick, Lauren Katz, and John Lehr, LA-based alumni of the fabled Chicago comedy group Ed, are joined by Toronto’s Sin City, which performs a fully improvised soap opera, and the Yellow Man Group, two women and one guy from Tokyo. John Bolger hosts. Athenaeum Theatre, 8 PM.

PM show by Georgia Pacific, an ImprovOlympic team that performs long-form improv in the dark. Second City, 1 to 6 PM. $5 (audience members can come and go throughout the day).

Solo Spotlight

Land of the Karaoking Improvisers features the music-comedy troupe Moctis improvising scenes based on karaoke songs selected by the audience. “Other, less seasoned improvisers would probably have made a hash of this format, but Moctis was able to turn out surprisingly rich scenes: their ratio of funny to unfunny bits was remarkably high. Even more impressive were their occasional serious character-based improvisations,” says Reader critic Jack Helbig. The program also features Chicago’s all-female troupe Sirens and the Liquid Radio Players from Hollywood. Playground, 10 PM.

Beer Shark Mice, featuring Saturday Night Live refugee Dave Koechner, is based at ImprovOlympic West in LA. WeirDass features Chicagoans Stephnie Weir and Robert Dassie performing scenes. On the Spot hails from Montreal. John Bolger hosts. Athenaeum Theatre, 7:30 PM.