1. We may have lost the recipe to our secret sauce

Ah, McDonald’s, the place where we feast upon Big Macs, Egg McMuffins and even the occasional sweet chili chicken McWrap. In the U.S., the fast-food chain, founded in 1948, boasts by far the largest annual restaurant sales--almost triple the volume of Subway, its nearest competitor, according to QSR magazine, a trade publication for the industry. And McDonald’s MCD, -1.03% is a fixture overseas, too, with restaurants in more than 100 countries.

In all, the company serves almost 70 million customers a day spread across 36,000-plus locations. In 2014, such feasting equated to revenue of $27.44 billion—more than the gross domestic product of about 90 individual nations.

But these days, things do not appear so golden at the home of the Golden Arches. McDonald’s recently reported that its net income in the fourth quarter of 2014 dropped by 21% from the year-earlier period. Nation’s Restaurant News, another major trade publication, went so far as to declare the chain’s overall 2014 performance as possibly the “worst in decades.”

The company’s troubles became a hot topic again when McDonald’s announced a management change in late January, with CEO Don Thompson retiring and chief global brand officer Steve Easterbrook filling the top spot. Industry watchers pointed to the company’s recent track record as the likely reason for the switch, though McDonald’s didn't go into detail about the cause in its news release. Thompson said, “It’s tough to say goodbye to the McFamily, but there is a time and season for everything.”

So, what’s behind the company’s woes? Some industry experts say it’s the Chipotle CMG, -0.80% factor: Fast-casual restaurants—like the Mexican chain—are seen as a healthier, fresher and contemporary-minded alternative to McDonald’s menu. (Chipotle’s earnings were up by 52% in the most recently reported quarter—and even that wasn’t high enough to meet Wall Street’s expectations.) There’s also the threat posed by small but much beloved burger-centric chains like Five Guys and Shake Shack, which are also generally considered fast-casual. (Shake Shack saw its stock price soar by more than 125% during its recent first day of trading.)

Things McDonald's won't tell you

Other experts point to a different culprit—namely, the now sizable menu at McDonald’s, which goes beyond burgers and fries to incorporate wraps, salads, gourmet coffee and even a yogurt parfait. (A recent Wall Street Journal report noted that the menu has grown from 85 to 120-plus items over the last seven years.) The cause for concern: the bigger the menu, the greater the potential for slow service—not exactly a plus in the fast-food game. Indeed, when QSR measured wait times at fast-food restaurants in 2013 as part of a continuing study, it found that service at McDonald’s was the slowest it’s been in 15 years, with a typical drive-through order resulting in a wait of 189 seconds. (Burger King was even slower, however.)

Whatever the cause for the decline, analysts say there may be no easy fix, since it’s challenging for such a sizable, established company to reinvent itself, especially for a millennial market that embraces the new. “It’s hard to point to one thing that’s going to get them out of this funk,” says Andy Barish, managing director at Jefferies LLC.

For its part, McDonald’s says it’s looking to the future, not the past: “2014 was a difficult year and performance fell short of our expectations, but it was also a building year and our management team is focused on regaining momentum in 2015,” says McDonald’s spokeswoman Becca Hary. She also says that McDonald’s is “beginning to see signs of forward progress in some of our critical (geographical) markets.”

Read 10 things Chipotle won’t tell you.

Fast-food workers and their supporters protest for higher wages inside a McDonald’s in Los Angeles. AFP/Getty Images

2. We call it an opportunity. Others call it a low-wage job

On its website, McDonald’s says it’s “proud of the jobs we create,” noting that it provides people “a way to buy that first car” or “enter the corporate world.” The company also notes that it offers flexible schedules and promotes diversity. Put it all together, McDonald’s says, and it encourages the 1.9 million people who work for the company world-wide (many of whom are employed via franchisees) to “make (their) own way, with challenging careers, quality benefits and the most opportunities around.”

Still, like most fast-food restaurants, McDonald’s has recently come under fire in the U.S. from labor advocates and its own employees for paying what they consider low wages. Fast Food Forward, a nationwide coalition of fast-food workers, has mounted a much-publicized “Fight for $15” campaign, demanding that McDonald’s and other chains pay employees $15 an hour, which it considers a “living wage” standard.

A 2013 University of California, Berkeley, study found that the median pay for front-line fast-food workers was $8.69 an hour. PayScale, a firm that tracks compensation data, puts McDonald’s median pay for food prep and service workers at a lower figure of $7.74 an hour, slightly below that of such competitors as Burger King ($7.96) and Wendy’s ($7.87). The federal minimum wage is currently $7.25 an hour.

“Higher wages at McDonald’s would be good for workers and would lift the economy,” says Kendall Feels, organizing director of Fast Food Forward.

McDonald’s spokeswoman Hary says the company and its franchisees “support paying our valued employees fair wages aligned with a competitive marketplace.” (In the U.S., 90% of McDonald’s restaurants are independently owned and operated by franchisees.) Hary also says that any increases in the minimum wage “should be implemented over time so that the impact on owners of small and medium-sized businesses—like the ones who own and operate the majority of our restaurants—is manageable.”

Actor Ryan Kwanten (left) chats with guests at a Ronald McDonald house in Australia. Getty Images

3. We may not be as charitable as we seem

McDonald’s philanthropic efforts are focused on its Ronald McDonald House Charities (RMHC) organization, which maintains 300-plus residences world-wide that provide housing for families when a child is being treated for illness or injury at a nearby hospital. “Our homes are filled with more than help, they’re filled with hope,” says RMHC on its website.

But some critics have questioned how generous McDonald’s is. A 2013 report, “Clowning Around with Charity,” authored by public-health lawyer Michele Simon, faulted the chain on many charitable fronts. The report said that McDonald’s provided only one-fifth of the funding for RMHC in 2012, despite the fact the organization is largely associated with the fast-food chain. (Other funding came through corporations such as Coca-Cola KO, -0.19% and Southwest Airlines LUV, -1.41% , plus individuals, according to the report.), In addition, the report said that McDonald’s gave 0.32% of its pretax profits to charity (based on a six-year average)—a much lower rate than other leading corporations of similar size, which gave an average of 1.01%.

In short, the report said, the chain’s “giving does not match its rhetoric.”

McDonald’s spokeswoman Hary didn't comment about the report. But at the time of the report’s release, McDonald’s senior vice president Bridget Coffing responded in a statement to ABC News by calling it “shameful and misleading.” Coffing added that the report “is a thinly veiled attack on our brand at the expense of the millions of families and organizations who have benefited from RMHC.”

These stalwarts endured; the Hula Burger did not. Bloomberg

4. For every success story like the Big Mac, we have plenty of Hula Burgers

Sure, McDonald’s has given the world plenty of beloved (and often imitated) menu items, including the Big Mac, the Quarter Pounder and the McRib. (The latter typically comes out for a select period annually to much fanfare, which has led Jimmy Kimmel to dub it the “Punxsutawney Phil of sandwiches.”)

But it has also given the world plenty of items that didn’t last the test of time. Among them: the Hula Burger (a meatless option with a slice of grilled pineapple substituting for a beef patty), McSalad Shakers (a salad served in a cup) and various pizza items (including, yes, a McPizza). More recently, the company introduced Mighty Wings (its version of spicy chicken wings), only to find that the public wouldn’t bite—literally.

To some extent, it’s all part of the business, say analysts, noting that fast-food chains must always try something new if they’re going to stay ahead of the competition. But the recent lack of a “breakthrough item,” as Baird senior research analyst David Tarantino calls it, has some on Wall Street concerned, particularly since competing chains have had menu hits of late.

McDonald’s points to the 2013 introduction of its Egg White Delight as a success story. The company also says it’s excited about the expansion of its Create Your Taste sandwich customization program. “We’re always looking at our menu and testing new food innovations,” says Hary.

Old meat created new headaches for McDonald’s in China. AFP/Getty Images

5. We’ve faced plenty of challenges overseas

McDonald’s has a strong presence in cities around the world, from A (Abu Dhabi) to Z (Zagreb), and its restaurant openings are often greeted with enthusiasm. But lately, the chain has run into headline-grabbing issues abroad. In China, its meat supplier was accused of selling items after they’d passed their shelf life. (McDonald’s wasn’t the only fast-food chain affected by the issue.) On top of that, the chain has faced increased competition in the world’s most populous country.

And in Russia, it’s been seemingly caught in political crossfire: After McDonald’s closed restaurants in Crimea following Russia’s annexation of the Ukranian region, the Russian government did a series of unscheduled inspections and closed several restaurants in Moscow, Sochi and other cities because of supposed sanitation issues.

Ultimately, such issues can affect sales and worry analysts. And that’s on top of economic concerns in countries where McDonald’s has a presence: Tarantino of Baird points to a recent tax increase in France and how that may be affecting consumers’ dining habits.

In a January conference call with analysts before his retirement was announced, Thompson pointed to ways McDonald’s is meeting various challenges overseas. In particular, he said business in Russia and China was in “recovery mode” and that the focus in those countries was on “winning customers back by emphasizing food quality.”

Morgan Spurlock (center): His weight gain was McDonald’s loss, Getty Images

6. We’re still getting blamed for the obesity epidemic

After documentary filmmaker Morgan Spurlock came out with “Super Size Me” in 2004, McDonald’s became something of the poster child for fast food’s role in America’s obesity epidemic. (In the documentary, Spurlock follows a diet of nothing but items from McDonald’s for 30 days, and gains 24 pounds in the process.) Since then, McDonald’s has instituted menu changes, including adding more food choices that nutritionists approve of and eliminating the “super size” option.

But the chain continues to be faulted for offering foods that many critics consider high in calories and saturated fat. Additionally, Center for Science in the Public Interest, a watchdog group focused on nutrition, has objected to the use of toys in McDonald’s signature Happy Meals, saying it ultimately encourages children to eat “junk food.”

In response to such issues, Hary says the chain is “committed to quality food, responsible marketing, and to providing information to enable our guests to make informed choices that fit their nutritional needs and lifestyle.” The company also points out that it recently added oranges and a lower-fat yogurt to its Happy Meal options and a side salad (as an alternative to french fries) to its Extra Value Meals.

Like its competitors, McDonald’s faces criticism over what’s in its beef patties. Getty Images

7. ‘Pink slime’ wasn’t our only controversial ingredient

When it comes to what goes in its food, McDonald’s has been transparent of late, launching a campaign, “Our Food, Your Questions,” that’s designed to address consumer concerns about ingredients. And the chain was out in front of many competitors in removing one controversial ingredient from its hamburgers—a finely textured beef dubbed “pink slime” by critics—in 2011. (Some 400 other retail, food-service and food processing companies are still using it.)

Still, that doesn’t mean everyone is letting the chain off the hook, as critics continue to express concern about a number of ingredients. Some point to the fact that McDonald’s beef isn’t hormone-free (some health advocates believe such beef poses a health risk, though the FDA maintains that the meat “is safe for humans to eat”). Critics also point out that McDonald’s uses azodicarbonamide—the “yoga mat” ingredient used to make bread fluffier (again, concerns have been raised about health risks, though the FDA considers the ingredient a “safe food additive”). Either way, it should be noted that McDonald’s isn’t alone in using such ingredients: For example, it’s been reported that many fast-food chains use azodicarbonamide, though Subway ditched it last year.

For its part, McDonald’s says it remains committed to being direct with consumers about ingredients, noting that since the October 2014 launch of the “Our Food, Your Questions” campaign, it has answered more than 30,000 queries from consumers. The company also says it has made a commitment to begin purchasing verifiable sustainable beef by 2016 (sustainable beef comes from producers who adhere to certain environmental and socially conscious standards). And it just announced that it will be sourcing antibiotic-free chicken starting within the next two years.

Some franchise owners are frustrated with the parent company. Bloomberg

8. Our franchisees aren’t always happy campers

As big as McDonald’s may be, it’s often its franchisees that are the “face” of the company--that is, they own most of the restaurants, especially in the U.S. But these days, some of those faces are wearing a grimace. In a recent survey conducted by Janney Capital Markets analyst Mark Kalinowski, some franchisees expressed frustration with the company, faulting it for “moving too slow” in making changes and launching “silly” marketing efforts, among other criticisms.

There’s also been concern that the menu is too large and results in slower service. And the Premium McWrap, introduced in 2013, has been a particular point of contention, since it takes a number of steps to assemble. “Our kitchen comes to a halt when we get an order for a McWrap,” one franchisee said last year.

McDonald’s spokeswoman Hary says the study captures the views of only a small number of the chain’s 2,000-plus franchisees.

‘Can’t talk: Gotta be in Louisville in 45 minutes.’ Getty Images

9. We won’t admit there’s more than one Ronald McDonald

McDonald’s has an international icon in its mascot, Ronald McDonald, a red-haired clown that has been part of the company’s marketing for more than 50 years. The clown makes appearances everywhere from McDonald’s restaurants to schools and libraries (he seems to be especially busy in Kentucky this year). He’s on Twitter, and even takes selfies.

But the one thing that McDonald’s won’t seemingly say about its mascot? That it employs more than one Ronald in its roster. Actually, the company keeps mum when it comes to many details about the clown—those who step into the Ronald suit must agree to never admit they do—and McDonald’s makes sure no two Ronalds ever appear together at public events, according to various published reports.

Today, McDonald’s doesn’t provide many more details about the clown, but it does clearly take pride in its mascot. Says Hary: He is “an ambassador for good and delivers messages to kids on safety, literacy and balanced, active lifestyles.”

Can you spot the Land, Sea and Air Burger? Getty Images

10. We’ve got a secret menu

Everyone knows about the Big Mac. But what about the Poor Man’s Big Mac? Or the Chicken McGriddle? Or the Land, Sea and Air Burger? These are all examples of McDonald’s menu hacks that are discussed online. Yes, just like Starbucks SBUX, -2.07% , McDonald’s has a secret menu of items that can be created by piecing together ingredients from established items.

Consider: The Poor Man’s Big Mac is a McDouble burger with extra lettuce and Big Mac sauce instead of the standard ketchup and mustard, according to the HackTheMenu website. (It’s called a poor man’s version because it runs about two bucks cheaper.) The Chicken McGriddle is simply a sandwich made with a McChicken patty in between two McGriddle cakes. And the Land, Sea and Air Burger? It’s a gut-busting amalgam of a Big Mac, a Filet-O-Fish and a McChicken sandwich. (Talk about a real whopper.) As the HackTheMenu site says: “The creators of the McDonald’s secret menu are those (who) dared to dream. Those who thought, ‘Hey, I can make this better.’ And that’s exactly what they did.”

Of course, some hacks require a little, ahem, assistance from the McDonald’s staff. (Others can be assembled tableside by the hacker.) The HackTheMenu website offers this key tip: “Be kind to the server.” Oh, and be prepared to explain how to assemble the hacked item. But indeed, some hacks are apparently established enough that no explanations are necessary. Either way, the hacked item might come with a charge for extra ingredients. As for the company’s official take on menu hacking, Hary simply says: “Our crew members will prepare your meal based on your preferences.”