How a Customer's Custom Order Created In-N-Out's Animal Style Burger

In-N-Out's Animal Style burger originated in the early 1960s when a customer watched an associate make a customized burger and asked for the same, giving rise to a famous off-menu item with a mustard-cooked patty, pickles, extra spread, grilled onions, lettuce and tomato. The creation helped launch a broader Not-So-Secret Menu of variations and cements the chain's culture of customizing burgers, even as the family-owned company grows to 400+ locations.