1. It was invented by a Pittsburgh-area franchise owner
In 1967, a small-time franchisee named Jim "MJ" Delligatti created a cheeseburger consisting of two 1.6oz beef patties, iceberg lettuce, pickles, American cheese, chopped onions, a special "Mac Sauce," and a double-cut sesame seed bun. At first, the burger was only available at three Pittsburgh McD's locations, but thanks to founder Ray Kroc’s enthusiasm, it went nationwide in 1968.
2. The middle bun was purely functional
As per Delligatti's original design, the Big Mac's center bun is used primarily to soak up the special sauce, keeping the sandwich from becoming a Big Mess.
3. You can DIY your own half-price Big Mac
According to a bunch of Reddit users -- as well as one very talented Thrillist writer -- ordering a custom McDouble (no mustard or ketchup, add shredded lettuce and special sauce) transforms the less expensive burger into a Big Mac and saves you a whole $2. You'll have to do without the middle bun, though, so be sure to double up on napkins.