Chick-fil-A still rules the roost when it comes to America's favorite chicken sandwich, but that menu item is quickly becoming an essential for quick-serve restaurants, and it's causing as big a stir as a fox in a henhouse.

Where's the beef?

Restaurant Brands International (NYSE:QSR) launched a chicken sandwich nationwide at its Popeyes chain on Aug. 12, only to see it sell out just two weeks later -- with no indication of when it will have enough to make a return.

Popeyes chicken sandwich

The Popeyes chicken sandwich is causing quite a stir in the fast-food industry. Image source: Popeyes.

Its popularity prompted Chick-fil-A to tweet out a reminder about who had the "original" chicken sandwich, which caused the master social media trolls at Wendy's (NASDAQ:WEN) to snark, "Y'all out here fighting about which of these fools has the second best chicken sandwich." When Popeyes answered that its rivals were looking "thirsty," Wendy's retorted, "lol, guess that means the food's as dry as the jokes."

While it may seem to be all in good fun, the chicken sandwich is Popeyes' biggest product launch in 30 years, and it means billions of dollars in sales to the fast-food industry as chains try to establish a new pecking order.

A call to action

Data from NPD Group's receipt-harvesting service Checkout shows that although hamburgers remain the top item ordered at fast-food restaurants, chicken sandwiches grew 3.3% over the 12-month period ending in July at 2.3 billion servings. Burgers fell to 6.4 billion servings.

Which is likely why McDonald's (NYSE:MCD) franchisees are worried that their burger joint doesn't have a chicken sandwich on its menu that can compete -- and why they're taking the matter into their own hands.

McDonald's does have a chicken sandwich and nuggets. But it's not the sort of "world-class chicken sandwich" the National Owners Association said the restaurant needs when it issued a list of actions this past summer that it believes McDonald's must take to become competitive again. 

The Wall Street Journal reported last week that the organization, which represents McDonald's franchisees, told its members it would rectify that and would unveil its own chicken sandwich at the group's annual meeting in Dallas later this month. "JFK called for a man on the moon. Our call should be a category leading chicken sandwich," it told members in a letter.

Above and beyond burgers

And it's not just chicken sandwiches that are whetting consumer appetites. The KFC chain, owned by Yum! Brands (NYSE:YUM), needed only five hours to be sold out of its plant-based Beyond Fried Chicken nuggets and boneless wings from Beyond Meat (NASDAQ:BYND) when it tested them at a single Atlanta restaurant. It said it sold as much faux chicken in that time period as it sells regular popcorn chicken in a week. Yum! plans to use the results of the pilot to determine whether the plant-based alternative should be rolled out more broadly.

Chick-fil-A nevertheless has catapulted past Wendy's and Burger King to become the third largest quick-serve restaurant in the country (Starbucks is second), with sales up 17% last year. 

Yet with Popeyes creating a sensation with its Southern-style sandwich (McDonald's franchisees say that was the first time Chick-fil-A "was forced to blink"), quality chicken sandwiches at your favorite local fast-food restaurant may no longer be as rare as hen's teeth.