When it comes to fast food, most people just order what’s on the menu. But in the U.S., customization is an art form. Regulars at major chains like McDonald’s, Starbucks, and Burger King know the secret: hidden menu items that aren’t advertised but can still be ordered if you know what to ask for. These creations often started as fan inventions that became legends through word of mouth. From monster burgers to sugar-loaded drinks, here are 15 fast food secret menu items you probably didn’t know about.

1. Burger King – The Suicide Burger
A favorite among big eaters, Burger King’s “Suicide Burger” packs four beef patties, four slices of cheese, bacon, and special sauce — all between two sesame buns. It’s not listed on the menu, but employees know exactly what you mean if you ask for it. Definitely not for the faint of heart, this burger is pure fast-food indulgence.