Why pizza, tacos, and Pop-Tarts have gone ‘crazy’

FORTUNE — At a certain point, we mature past eating food on a dare. If someone describes something by using the phrase, “That’s crazy,” you generally wouldn’t put it in your mouth. But some food companies are making money hand over fist on products that they freely admit you have to be kind of nuts to eat. Why does this work?

First, let’s take a look at the masters. Yum Brands (YUM), which owns KFC, Taco Bell, and Pizza Hut, has nailed this formula. On April 3 the company introduced its “Crazy Cheesy Crust” Pizza, which it deemed “an explosion.” In Pizza Hut’s own language from the press release:

“The mere name of the pizza is quite fitting. It’s Crazy — featuring 16 dough pockets at its outer edge — Cheesy — each pocket is filled with a blend of five Italian cheeses — and Crust(y) — the element of a pizza that Pizza Hut has a rich tradition of revolutionizing all around the world.”

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Yum, it would seem, is bilingual in “Crazy.” During its fourth-quarter earnings call on February 5, President Richard Carucci trumpeted the success of its “Doritos Locos Tacos,” — essentially a meat, cheese, and salt bomb wrapped in a taco shell made from a Doritos chip. Yuck, right? Wrong. Genius.

“During 2012, Taco Bell sold 325 million Doritos Locos Tacos,” Carucci said. “That’s more tacos than there are people in the United States and makes it one of the most successful product launches in [quick service restaurant] history.

Companies besides Yum have gone the crazy route. Four Loko was wildly popular before the FDA deemed it dangerous, banning the caffeinated sugar booze in 2010. Kellogg’s (K) Pop-Tarts breathed life into the brand with their “Crazy Good” campaign, which launched back in 2004 and is still  going today. Kellogg’s maintains its marketing strategy — in which “crazy” is a positive modifier — by various means including sponsoring concerts by the likeable, saccharine Carly Rae Jepsen

The word “crazy” works particularly well for food because it hones in on the current zeitgeist. “I think ‘crazy’ is definitely skewing towards millennials and even younger,” says Andrew Pierce, U.S. President of brand consultancy firm Prophet. “If you do a Google Image search for the word ‘crazy’ (please turn your safe search filter ON) all you see is Homer Simpson, cats, and cartoon characters.” These are things young people like.

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Thus, “crazy” food can mean fun, creative food, which lines up with our evolving national taste. “What’s happening is that the American palate has moved from boring to bold,” says Nancy Brown, a partner at branding firm CBX.  About six years ago, she says, marketers went after teen males by calling products “extreme.”

“I think ‘crazy’ is what ‘extreme’ was because ‘extreme’ has kind of run its course,” Brown says. And trends do. Companies should beware, says Pierce, because just as “OMG” is now old news in the youth lexicon, “crazy” too, shall pass.

These promotions tend to take that factor into account. Unlike Doritos Locos Tacos, the new “crazy” crust pizza is billed as a limited-time-only engagement. These can be flash-in-the-pan hot items that companies can yank from the shelves before the branding strength of “crazy” runs out.

Worst-case scenario, these promotions create buzz for the brand in the fiercely competitive quick-service restaurant category, which always runs the risk of becoming mundane. If, like Taco Bell, you hit gold, the sales boost is just Dorito-encrusted icing.

So “crazy” works on two kinds of consumers, suggests Pradeep Chintagunta, a marketing professor and consumer behavior expert from the University of Chicago’s Booth School of Business. One is the heavy junk food consumer, generally young and male, who is looking for new ways to spice up his favorite foods. Convincing him a product is “crazy” can get him in the store or at least generate buzz.

But the second target group for “crazy” food marketing reflects an interesting trend in our national food psyche. That is, people tend to perceive their eating habits as a kind of balance, says Chintagunta. And many consumers are waking up to the country’s issue with obesity-related heart disease and diabetes. They really are working hard to eat healthier. So when they want to splurge, they don’t just want a Snickers bar, they want something so crazy that it balances out the rigidity of the rest of their diet.

“People like to balance virtue and vice,” says Chintagunta.  “They’ll say, ‘During the week, I was a good person. I ate my lettuce, I ate my salad. Now it’s the weekend, and I want to cut loose a little bit. If I try something, I want to try something a little bit crazy.’”

Lucky for them, there’s a cheese-pocket filled pizza with their name on it. Problem solved.

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