Everybody loves to share in a good secret, and the experience is all the more delicious when food is involved. That’s why “secret menus” at chain restaurants have become so popular in the past 15 or 20 years.

Secret menu items aren’t exactly on a menu, secret or not, at least not a written one. They’re simply combinations of ingredients that restaurants already have on hand, put together in ways that may not be officially sanctioned but that don’t take much extra work on the part of employees and tend to make customers very happy. And these are the restaurant chains with the happiest customers.

Knowledge of these off-the-menu creations, which may cost extra (but don’t always), is shared by word of mouth or through social media — or at least it was until almost everybody got in on the secret, which seems to be the case today.

Click here to see secret off-the-menu items to order at your favorite chains.

Moms across America, for instance, now know that McDonald’s will make their picky little eaters a grilled cheese sandwich on request. It doesn’t take much to figure out that if Dairy Queen serves root beer and vanilla ice cream, they will probably put them together for you into a root beer float. And is there a burger lover in America who doesn’t know about the “animal style” offering at outlets of that beloved West Coast chain?

Bear in mind that some chains actually publicize their secret menu items, while others deny that they exist at all and even discourage their staff from making them. It’s always worth trying, though. Just ask politely if they’re available (bearing in mind that when places are very busy, they might not have time to grant your request).

24/7 Tempo has assembled a list of some of the country’s best secret menu foods and beverages, representing 20 different chains, from Arby’s to Wendy’s, with plenty of everybody’s favorites in between — including fast food chains with the best breakfast menus.