McDonald's is the most well-known fast food restaurant in the country, if not the world. There's no mistaking its golden arches, creamy McFlurries, or iconic Big Mac. While you might think you know everything there is to know about the chain, there are a lot of pieces of McDonald's history that might surprise you. From Happy Meal toys to recipe changes, here are all of the surprising things you didn't know about McDonald's.

The Largest McDonald's In The World Has An Arcade And Aquarium

This massive McDonald's is located near Universal Orlando Resort in Florida. Not only is the restaurant open 24/7 and 365 days a year, but the second floor—yesm second floor—has an arcade and aquarium.

There Have Been A Lot of Happy Meal Toys Over The Years

"I think early on, the flying hamburger was really popular," said McDonald's Archivist Mike Billington. "We also had puppets that were for the McDonaldland characters." There have also been plenty of Collector's Meals, which feature collectible items like the Beanie Babies in the late 1990s. McDonald's just launched a new Collector's Meal featuring six cups that depict past collectibles.

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McDonald's Used To Serve PB&Js

Way back in 1940, McDonald's had a much different menu. The biggest difference? Customers could order a peanut butter and jelly sandwich. Realizing that hamburgers performed much better, the chain shut down in 1948 and reopened with burgers as the star menu item.

Before Chicken McNuggets, There Were Onion Nuggets

Onion Nuggets were introduced in 1975, but they didn't last on the menu for long. They were like onion rings in the shape of nuggets. While onion nuggets didn't work out, Billington said that McDonald's then launched Chicken McNuggets.

It's True, McDonald's Coca-Cola Does Taste Different

Ever wonder why McDonald's Coca-Cola tastes so good? Most places get the syrup for their Coca-Cola delivered in plastic bags, but not McDonald's. Instead, it comes in stainless steel vats, which protects it from things like light, heat, and oxygen.

The Big Mac Wasn't Always Called The Big Mac

When it was launched in 1967, the burger was called the Aristocrat. It was referred to as The Blue Ribbon Burger before being called the Big Mac.

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In The U.S., There Are More McDonald's Than Hospitals

There's over 14,000 McDonald's restaurants in the U.S., compared to just over 10,000 hospitals.

There's Only One McDonald's That Doesn't Have Golden Arches

A McDonald's location in Sedona, Arizona, doesn't have golden arches, but turquoise arches on the front of its building.

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McDonald's French Fries Haven't Always Followed The Same Recipe

McDonald's is known for its fries, but it hasn't always used the same recipe. Prior to 1990, they were fried in beef fat. Due to health concerns, McDonald's then began using a vegetable-based oil. Of course, people complained that the fries didn't taste the same, so they changed the frying oil to contain beef flavoring. The flavoring contains hydrolyzed wheat and milk, so McDonald's fries aren't gluten-free or vegan.

Every McNugget Is One Of Four Shapes

Yep, every single McDonald's McNugget is either the shape of a boot, ball, bone, or bell.

McDonald's Has Nine Schools

McDonald's operates nine Hamburger Universities. They're training facilities where students learn all the in and outs of working at McDonald's. They graduate with a degree in Hamburgerology.

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McDonald's Is The Largest Toy Distributor In The World

McDonald's reportedly sells 5,000 Happy Meals every minute. And with a toy bundled in each, there's no wonder it's the largest toy distributor in the world. That's 1.5 billion toys globally per year.

The Filet-O-Fish Was Introduced For Religious Reasons

During the season of Lent, many Catholics abstain from meat on Fridays and eat fish instead. Worried about lagging burger sales, McDonald's introduced the Filet-O-Fish in 1962, and it was on menus nationwide by 1965.