The comedy titan stops by to sing an R-rated duet with Paul and discuss his directorial debut, 'Old Dads.' He also opens up about his triumphant homecoming as the first comedian to ever play Boston's Fenway Park, how the mean streets of Bean Town made me an expert at handling hecklers, what it was like to have legendary author David Foster Wallace as a teacher, and how conspiracy theories helped spark an unusual hobby: flying helicopters.  See omnystudio.com/listener for privacy information.