For years, In-'N-Out has made it clear that they have a menu that's unavailable to the public's eye (although at this point they call it the not-so-secret menu), but it appears some fast food secret menus have really stayed in the dark for so many years, but it's time for them to come into the light!

A few days back, fast food secret menus became a trending topic worldwide after a Reddittor who identified himself as a McDonald's manager revealed the golden arches had a few menu items that were kept from the public eye, but it turns out they're not the only major chain to follow this rule.

According to The Daily Mail UK, other fast food secret menus include fried chicken giant KFC, its Yum! Brands sister restaurants Taco Bell and even Subway, as all of these have been recently revealed to be in on this new trend.

Cosmopolitan reports on some of the most interesting fast food secret menu items, such as the surprising fact that KFC's secrets are actually quite varied, including the Ultimate Zinger (an Ultimate Burger that changes its two smaller fillets for a Zinger one), the Double Down (which has bacon, two different types of melted cheese, and the Colonel's secret sauce between two chicken fillets) and the Zinger Stacker (two Zinger Fillets, two slices of melted cheese, spicy sauce and chili relish - although it's only known that it's sold in Australia).

As far as fast food secret menu items in Burger King, The Mirror reports there's a Veggie whopper available, which is to say a classic whopper that replaces the patty for a vegetarian one; the aptly named Suicide Burger has four beef burgers, four slices of cheese and four of bacon between buns while the Frings burger mixes half fries and half onion rings.

Other fast food secret menu items include Subway's Pizza Sub - a sandwich with pepperoni, tomato sauce and cheese - and Taco Bell's Incredible Hulk (a five-layered burrito replacing nacho cheese with guacamole), Enchirito (a combination of enchilada and burrito with beef, cheese and beans topped with red sauce) and the Cheese Gordita Crunch (which gets the classic beef taco inside a Gordita shell, separating both shells with melted cheese).

The chains have all denied these fast food secret menus - so you might have to try them on your own!