An Ask Me Anything (AMA) thread on Reddit confirmed that McDonald's can serve up "secret menu" items just like any customized order.

A McDonald's shift manager from Glasgow, Scotland, acknowledged the existence of the menu, saying that rather than being an official list of items, it is simply possible to customize any regular menu item.

The manager, who goes by the Reddit username orchidhibiscus, explained that any McDonald's sandwiches may have ingredients removed or added at a customer's request. The custom meal will be picked up by the cooks as a "grill order." The secret menu, he adds, is a random listing of hackable burgers at McDonald's that will cost a customer more money for any ingredients that are added.

Some of these custom sandwiches include the Land, Sea and Air Burger which hybridizes a Big Mac, McChicken and Filet-O-Fish into one. A McGangBang places a McChicken inside a double cheeseburger.

A Business Insider investigation into whether this secret menu exists revealed that although the menu is not an actual thing, these custom burgers may be produced at the restaurant's discretion.

The manager also urged Reddit users to stay away from the grilled chicken, saying it's "horrible" food that is "a bit gelatinous" after being defrosted and steamed.

Reports indicate restaurants such as In-N-Out, Shake Shack and Wendy's also have secret menus.