In 1965, Alan Stillman was a young man living in Manhattan, who, in his own words, was “looking to meet girls.” The bar restaurant he founded, T.G.I. Friday’s, began life as a public cocktail party — the first neighborhood joint to welcome both men and women alike, with the express motive to unite the two. Forty-five years later, Stillman’s singles’ bar in the Upper East Side has metamorphosed almost beyond recognition, spawning a landscape of casual dining franchises that redefined the American idea of the restaurant.