Burgers
Filet-O-Fish
A Friday problem solved with a fried fish square.
A fried fish sandwich on a steamed bun with tartar sauce and half a slice of cheese, created in 1962.
Lou Groen ran a McDonald's in a heavily Catholic neighbourhood of Cincinnati and watched his Friday sales collapse during Lent, when observant customers abstained from meat.
He proposed a fish sandwich. Ray Kroc was pushing a pineapple-and-cheese alternative he called the Hula Burger. They agreed to sell both on one Good Friday and keep whichever won. The Filet-O-Fish won decisively and went national in 1965.