When It's Always Sunny in Philadelphia returns this week with "The Gang Saves the Day", the series celebrates its 100th episode. FX has released a trailer and six photos for this series milestone, which focuses on the gang getting caught in the middle of an armed robbery, where each of them is forced to explore how they react in extreme situations. Take a look at the latest footage and photos, and be sure to tune in to FXX this Wednesday at 10 PM to celebrate with the Paddy's Pub crew.