In-N-out Burger. 6:00 p.m. I say to my girlfriend in line beside me, "I want a burger, but I'm tired of all that bun." A bearded 20-something walks past and says, "protein style, lady." Confused, I look at the menu. No mention there. But the cheerful teen behind the counter nods approvingly and asks, "you want it that way, wrapped in lettuce, not a bun?" Great idea, I say.

And just like that, I'm in on the secret. Menu, that is. Turns out, that's just one of the many so-called "secret menu" items at this famed California fast foodery. (They're posted on the website, though not in the brick and mortar spot.) And it's only part of a bigger feast fad known as "the secret menu." Try the McBruschetta at the Golden Arches (toasted tomatoes, onions, bun), the Naked Chicken at Popeye's (meat, no breading), or the Short Cappucino at Starbucks (more intense brew served in a kid's cup).

This is strictly grass-roots stuff, however. Most of these items are not official. (In-N-Out Burger executives deny a secret menu, calling the Web list a customer service.) They're the fruit of enterprising, empowered customers taste-testing their way into new territory on their local fast-food turf. The top combinations rise like cream to become unofficial "secret menu" items that spread through word of mouth and repeated orders.

Big shots in swanky nightspots have always been able to order a sirloin seared to personal taste. But custom eats for the common man are relatively new. According to a number of food experts, it's part of a feasting frenzy fed by Internet chatter and the explosion of foodie reality TV shows – "Top Chef," "Hell's Kitchen," etc. – that makes everybody feel like a gastronomic insider, no matter their budget.

The secret menu appears to be on the upswing, so I decide to taste-test this theory on local terrain. I press Monitor intern, Alison Tully, into service – she hits Jamba Juice and Starbucks; I take the rest.

In-N-Out, which used to be the Golden State's own fast-food secret with its freshly stamped fries and authentic shakes, is known for its helpful servers. It's also famous for offering a select, few items on that glowing outdoor board – basic burgers, shakes, sodas, and fries. I speak my secret desires – in proper lingo gleaned from the website – into the squawk box, "a two by two, animal style, and a neopolitan." Translation: a two-patty mustard burger, with everything, including extra sauce and grilled onions, and a three flavor shake (chocolate, vanilla, strawberry). The box cheerily blasts back, "Pay at the first window, please. Have a nice day!" Say goodbye to the days of "Five Easy Pieces," when Jack Nicholson couldn't get toast at a coffee shop because it wasn't on the menu.

Things get stickier for Alison at Starbucks. "We don't have a secret menu," says the barrista, who won't give his name. He points to the overhead menu. A nicer cohort nearby rolls her eyes and offers Alison "anything she wants," which is of course, the soul of the secret menu.

Over at Jamba Juice, however, she hits the sweet spot, scoring the distinctly non-health-bar-sounding White Gummi Bear (a complex smoothie concoction that tastes like the rubbery candy), Strawberry Shortcake, and Push Pop smoothies, no questions asked. Apple-cheeked teen server, Daryl, says "the majority of our customers order secret menu stuff."

Why is this, I ask a national food expert by phone. "Cachet," answers Joyce Weinberg, president of New York Food Tours, a culinary-adventure firm. "Who doesn't like to be in the know?" Besides, she adds, this is the "my" generation. "They've all grown up thinking they can have the world their way."

It's a win-win, says Paul Dholakia, an associate management professor at Rice University in Houston. It's pure genius from the restaurant's point of view, he adds. "It's the best way to get around the barriers we've all put up against commercial messages that I've seen in a long time. People actually seek these things out."

Just like me, and now… Alison. But suddenly I need to know – how far can this go? I try out my new, have-it-my-way persona at a local mall smoothie counter, Surf City. I peruse the menu, then order what I dub the "Berry Pleaser."

"Make me a medium with blueberries, strawberries, raspberries, and a hint of mango." The server squints, then hauls out three brightly colored jars. She dumps red, blue, and yellow globs into a blender. One short burst of whirrr! later and I give her an approving nod. All secrets should be so delicious.