If you're a fan of It's Always Sunny in Philadelphia, then you know the gang is always trying to push the envelope. So what's in store when the comedy returns in September? A big Mac — literally. Rob McElhenney packed on 50 lbs. for the new season, and if this promo is any indication, the new season will revolve heavily around Mac's new food obsession (something tells us that Charlie, Dennis, Dee, and Frank are going to have a field day with this one). Check it out before the show returns on September 15.