Vince Vaughn, Aziz Ansari, Stephen Merchant and Bill Engvall are booked to perform at the fourth annual Just For Laughs festival in Chicago, TBS said Tuesday. Also on the bill for the June 12-17 event are Billy Gardell, John Pinette, Patton Oswalt, John Oliver, Kevin Smith, Mike Birbiglia, Jeff Ross, Amy Schumer, The Dan Band and Henson Alternative\'s Stuffed and Unstrung. Tickets for the festival are to go on sale Saturday.