Fans of the Day Man rejoice! EW has learned that FX comedy It's Always Sunny in Philadelphia will return for a 4th season. The half-hour show, about four friends and the Irish dive bar they operate when not getting into unwholesome trouble, is scheduled for a 13-episode run. An air date has not yet been determined, but the writing staff is already sketching out story ideas with production tentatively set to begin in June. The main cast will return in its entirety, including Danny DeVito as the gang's twisted father figure.