Wendy's pretzel-bacon cheeseburger is the latest -- and certainly won't be the last -- in a long line of extreme experiments from fast-food brands. Here are some greatest hits of the last few years, guaranteed to torpedo any diet:
Zombie Burger -- The Walking Ched
This Iowa burger joint's Walking Ched is more likely to leave diners comatose than upright. Its buns are breaded, deep-fried mounds of mac and cheese, and sandwiched between the "buns" are a double cheeseburger with bacon, cheddar cheese, caramelized and raw onions, mayo and -- yup, you guessed it -- an extra scoop of mac and cheese. In case the buns weren't enough.
Dunkin' Donuts -- Glazed-doughnut breakfast sandwich
Doughnuts as sandwich bread? Dunkin' introduced its donut breakfast sandwich, with sausage and beef between two glazed doughnuts, in June as a permanent addition to its menu. At only 360 calories, the sandwich-dessert mashup has been getting solid reviews for mastering the salty-sweet paradigm.
Taco Bell -- Waffle taco
If a waffle doesn't sound like the natural extension of a taco, think again. In May, Taco Bell began testing sausage and scrambled eggs in a waffle in Southern California, a potential extension of the breakfast menu it launched in 2011. It's a departure from how competitors are approaching the breakfast daypart; McDonald's, on the other extreme, rolled out a more-healthful Egg White Delight McMuffin in April.
Sonic -- Peanut-butter-and-bacon shake
As part of its "2013 Summer of Shakes," Sonic is offering 25 shakes including the peanut-butter-and-bacon shake -- a mixture of peanut butter and real bacon topped with whipped cream and a cherry. The minute amount of bacon provides a pinch of saltiness to the sweet dessert.
Starbucks -- Bavarian-style pretzels
In May, Starbucks went German with its two Bavarian pretzels offerings in stoneground Dijon and asiago and cheddar. The stoneground Dijon has honey to highlight the mustard flavor, and the cheese or mustard are layered directly into the dough so there's no mess. The coffee chain acquired La Boulange Bakery in 2012, so experimental baked goods may be the new norm.
Krusty Burger -- Clogger Burger
Universal Studios' long-awaited Fast Food Boulevard based on "The Simpsons" opened in May, and its Krusty Burger -- the show's running satire of fast-food chains like McDonald's and Burger King -- serves the sitcom's aptly named Clogger Burger: two burger patties, bacon, secret sauce, cheese sauce, tomato and lettuce on a bun.
Pizza Hut U.K. – Hot Dog-Stuffed Crust Pizza
If you've previously attempted to cook a hot dog into your pizza crust and been unsuccessful -- a heroic quest we're sure many have tried -- Pizza Hut U.K. has the cure. The chain's brethren across the pond serve a hot-dog-stuffed-crust pizza with mustard drizzle. If it sounds all-American, don't get too excited; Pizza Hut has no plans to introduce the frankfurter-pizza amalgamation in the U.S.
McDonald's Philippines -- Chicken McDo
It's fried chicken served with your choice of steaming rice or spaghetti. We're still trying to discern if this Philippines exclusive is competing with KFC, Olive Garden or your mom.
Pizza Hut Middle East -- Kit Kat Pops
Miniature Kit Kat candy bars covered in pizza dough and coated liberally with sugar. This 2012 menu addition in the Middle East is either a breadstick wannabe or a genius dessert.
KFC Philippines -- Mac-and-cheese bites
The Philippines is the only country to enjoy KFC's deep-fried balls of mac and cheese mixed with bacon. Introduced in 2012, KFC sells them as bite-size treats in packs of five. No plans yet to bring these cheesy poppers stateside.
Burger King -- Bacon sundae
BK's bacon sundae is a blend of vanilla soft serve with fudge, caramel, bacon crumbles and a delectable piece of bacon chilling on the edge like an umbrella straw. It didn't stick around past the summer.
Jack in the Box -- Bacon milkshake
Jack in the Box rolled out its bacon milkshake in early 2012, a frothy concoction of vanilla ice cream, bacon-flavor syrup, whipped topping and a cherry. Unlike BK's bacon sundae, and Denny's maple-bacon sundae of 2011, the Jack in the Box variety doesn't rely on real bacon. It's not bacon-colored and doesn't even come with bacon shavings on top. Perhaps it's the dessert for the moderate consumer of bacon?
CiCi's -- Mac-and-cheese pizza
One of CiCi's experimental 2011 pies features pasta, cheese sauce and pizza cheese spread across a pizza crust. Based on reviews, it's a popular grab in the chain's buffet line. Also available: CiCi's cheeseburger pizza with ground beef, cheese, pickles, mustard and ketchup.
KFC -- Double Down
In April 2010, KFC ditched the bread bun in favor of fried chicken. The Double Down used chicken filet to sandwich two pieces of bacon, two slices of cheese and sauce. The limited-time offer got more buzz than any test market item in KFC history, according to the company, and clocked in at a surprisingly low 540 calories -- fewer than McDonald's Big Mac.
Friendly's -- Grilled-cheese burger melt
On the heels of KFC's heart-attack-in-a-wrapper sandwich, Friendly's in 2010 unveiled its own behemoth, subbing in a grilled cheese sandwich for each of a burger's bun slices. That's right: a grilled-cheese sandwich, lettuce, tomato, beef patty and another grilled-cheese sandwich sold as one gargantuan menu item. This limited-time concoction didn't do your waistline any favors at 1,500 calories and 97 grams of fat.