Stories from the set

Charlie Day, who played Charlie, is married to Mary Elizabeth Ellis, who played the Waitress.

In the summer of 2008, Kaitlin Olson suffered a serious injury, so during the filming of season 4 the actress was still recovering. Because of this, the scene of Sweet Dee's fall was moved from season 4 to season 5.

During its first two seasons, "It's Always Sunny in Philadelphia" was one of the lowest-budget series in television history. As the show's popularity grew, its budget increased.