Rob McElhenny and Glenn Howerton -- the two creators and stars of It's Always Sunny in Philadelphia -- along with FX President John Landgraf, tell the unlikely origin story of this off-beat comedy.

Banner image: (L-R) Charlie Day, Rob McElhenney, Glenn Howerton at the season premieres of FX's It's Always Sunny in Philadelphia. Photo by Brian Dowling/PictureGroup/FX 2012