This blog post tells the story of Lou Groen, a McDonald's franchisee who invented the Filet-O-Fish sandwich in 1962 to save his struggling restaurant in a predominantly Catholic area, where customers abstained from meat on Fridays. Groen faced challenges in recipe development and competition, but ultimately succeeded, leading to significant sales for McDonald's. His innovation not only saved his franchise but also led to the fish sandwich becoming a staple menu item for McDonald's.