Secret menus. McDonald's (MCD) has one. So do Burger King (BKW), Subway and most other fast-food chains. These are items that, for various reasons, are not on the regular menu, but can be had if you know what to ask for.
Mostly people find out through word-of-mouth and through social networks, but there are also a couple of web sites that track these offerings.
Maybe the oldest practitioner of the secret menu is In-N-Out Burger. And it's not much of a secret: the company even posts six items on its website that are not on its menu. Try the protein burger; it's wrapped in lettuce instead of a bun.
Elsewhere, many of these 'secrets' are not for the faint of heart, or for dieters.
If you're really hungry, go to McDonald's and ask for the Monster Mac. That's a big Mac with eight patties. McDonald's also offers some seasonal items. Available this month only, the McLeprechaun, which combines the Shamrock Shake with a chocolate shake.
Burger King offers a secret Suicide Burger. Your cardiologist will love this one: four beef patties, four slices of cheese, bacon, and, of course, the special sauce. More sensibly, BK also offers a Veggie Burger.
If you love the mashed potatoes at KFC (YUM), don't get them as a side. You can put them, with or without gravy, on top of your sandwich.
Subway has a pizza: tomato sauce, cheese, either pepperoni or salami, on your choice of bread. Chipotle (CMG) has a super-sized Burritodilla and a Quesarito, which weighs in at more than 1500 calories. Even Starbucks (SBUX) plays this game: You can get the Zebra Mocha, which combines white chocolate and chocolate mocha. There's also the Cake Batter Frappuccino and the Chocolate Dalmatian. Panera Bread (PNRA) has recently jumped aboard with several items for people whose diets do not include bread. Think of them as Panera bread-less.
So why do these chains offer 'secret' items? Well, for one thing, it's cheaper. They don't have to alter the official menu, and they can drop the items at any time. Also, it's a way to build buzz and loyalty. Some customers like the idea that they know something that others in line don't.