In-N-Out's Animal Style burger traces back to the early 1960s, when a customer spotted an associate's custom creation and asked for one just like it.
https://www.foxnews.com/food-drink/in-n-out-popular-burger-style-started-customer-request-decades-ago
https://www.foxnews.com/food-drink/in-n-out-popular-burger-style-started-customer-request-decades-ago