Executives at Starbucks don't market to children. The coffee company seems to have plenty of loyal grade-school-aged customers, anyway, at least in the US, because of a few drinks that lend themselves to kid-friendly twists. Ask a barista for a cotton candy Frappuccino, for example, and she'll create this unofficial favorite by adding raspberry syrup to a Vanilla Bean Frappuccino, which is one of the company's official offerings, an icy and sweet blended drink topped with whipped cream. Knowing how to ask for these twists, or "secret menu" items, is half the fun.

What a "genius" marketing strategy, Financial Times writer Gillian Tett gaped when her young daughters sought out cotton candy Frapps at a Starbucks in Manhattan this summer. Bloomberg View contributor Mohamed A. El-Erian had the same experience with his 11-year-old daughter in May. He, too, called this "a brilliant marketing move on the part of Starbucks," albeit one the company didn't have to spend any resources on. Starbucks CEO Howard Schulz refers to the secret menu phenomenon as a pleasant surprise: "I'm stunned and amazed at the concoctions that people order with our Frappuccino," he said in June. "I never imagined it and the secret menu that has developed as a result."

Secret menus exist at McDonald's, Taco Bell, Burger King, Chipotle, Jamba Juice, and other restaurants, too. They're hardly secrets, of course, but the word "menu" connotes a curation of sorts, intentionality on behalf of the food establishment—and that's at odds with the origin stories of most of these items.

It just takes one brave customer to create a sensational menu item

California fast-food chain In-N-Out Burger, made famous by the existence of its not-so-secret-anymore menu, won't take credit for its signature "animal-style" fries and burgers (customers can ask for any regular menu item to be made "animal-style" and it will come topped with melted cheese, onions, and a special sauce). In-N-Out Vice President Carl Van Fleet says the term first surfaced in the early 1970s, but the company has "no clue" who said it first. "We truly never sat in the office and decided to name variations on our burgers," he told Fast Company in December 2013. "In fact, we don't see ourselves as having a 'secret menu' at all. The so called 'secret menu' items are simply variations in methods of preparation for our basic menu items. We only serve burgers, fries, and drinks and we've always made each burger exactly the way a customer orders it."

Such is the case with nearly every fast-food or fast-casual chain's secret menu: it's a set of accepted menu hacks, or modifications, and some special lingo. It's customer-driven, which today also means social media-driven. The daughters of the Financial Times and Bloomberg View writers, mentioned above, took photos of their cotton candy Frappuccinos at Starbucks and shared them with friends via Instagram and text messages. Seventeen, a magazine for teenage girls, regularly shares secret menu recipes with its readers on Facebook and Twitter.

When requests for especially difficult-to-make or inconvenient modified items become widespread enough, then customers are empowered to ask for these things without feeling like they're actually inconveniencing their servers.

Fancy names are fun, but not foolproof

Intense customization and special lingo have long been a part of the Starbucks experience, for example, and it's no secret that there are, according to company PR rep Linda Mills, more than 170,000 possible unique drink combinations. But there's no thrill associated with ordering "four shots of espresso plus four pumps of white chocolate syrup over ice, in a Grandé cup, with milk." What gets customers excited is asking for a complete recipe that can stand alone under a special name, just like a regular menu item, but one that only a few customers know exists. "Liquid cocaine" is what that Grandé iced milky thing with eight pumps of espresso and white chocolate is called.

But these special names don't always register at the counter. Baristas aren't trained to make blueberry muffin Frappuccinos or Butterbeer Lattés, so anyone ordering an off-menu item must also be willing to walk the barista through its creation. Then, after producing the drink, the barista may have a head-scratching time deciding how much to charge for it. This may be where the thrill of the secret menu falls away and the customer is rendered an entitled jerk for holding up the line.

Customizing without aggrandizing

Ordering off-menu at full-service restaurants used to be a bit of a power play: tolerable if done by a friend of the establishment or someone who otherwise warranted appeasement, but a faux pas coming from an average customer. And the concept of fast food rested on a distinct lack of options; rather than catering to unique preferences, the first fast-food franchises succeeded by offering signature, always-built-the-same-way items that happened to have universal appeal.

That dynamic is being reversed as average consumers expect more customization and more flexibility from fast-casual chains but are content with increasingly limited options—or no freedom in food choice at all—at fine dining establishments, where prix fixe menus are more common. Single-item restaurants are also popular in the US. Meanwhile, Starbucks, Chipotle, Jamba Juice, and similar places have expanded their offerings by acquiescing to creative customers and those with dietary restrictions.

Panera Bread tried to capitalize on this trend last year by creating an official "hidden menu" that featured low-carb, high-protein items. The idea was right: it was about better accommodating a supposedly small group of customers that wanted to eat at Panera without derailing their diets. But Panera announced the menu's existence with perhaps a bit too much flair, and some observers assumed that the chain was poorly mimicking the In-N-Out model—trying to fake its way to coolness.

Regardless of how secret or how carefully curated (versus creatively crowdsourced) their menu items are, being able to offer more unique food modifications than their competitors is increasingly important for quick-service brands. Reporter Mark Wilson, who spoke to In-N-Out's Carl Van Fleet for Fast Company, also interviewed Chipotle spokesman Chris Arnold about the role of secret menus and custom orders in the fast-food industry. "I think of it as the customer's the brand manager," Arnold told Wilson.

The most secret menus of all are impossible to hack 

It's rare, but still possible, to find secret offerings that are not menu hacks but original items created by the restaurant. In some cases, these are dishes that have been discontinued from the regular menu but will be resurrected upon request, as New York-based foodie Kat Manalac observed when she spent a year hunting down the best off-menu dishes and revealing them on the website HiddenMenu.com. Manalac asked chefs directly "if they served anything that was off-the-menu, or if there was anything they liked to make for themselves." The answer was frequently yes, though the chefs wouldn't always share the specific foods or the code words with her. At The American Grilled Cheese Kitchen in San Francisco, for example, Manalac got to taste a fizzy, fruity drink that chef Nate Pollock said he made for regulars—but he wouldn't tell her the name of it or how people ordered it.

The difference between a custom order and a truly secret item is about a sense of adventure and a willingness to surrender to a true recommendation by the people who know best. Like a real secret, it's about trust. Customizing is easy and fun, but the best secret menu hack of all might be the sweet success of taking a risk and tasting its reward.