Back in the day, drive-in restaurants were a dime a dozen. But they’ve mostly gone the way of the drive-in movie theater, with one notable exception: Sonic Drive-In. As the biggest chain of drive-in restaurants still in existence, Sonic serves 3 million customers across 44 states every day. Even if you're a loyal consumer of cherry limeades, here are a few facts you probably didn't know about "America's favorite drive-in."

1. Sonic was originally just a root beer stand.

Restaurant founder Troy Smith tried his hand at running a number of restaurants, from diners and steakhouses to a root beer stand in Shawnee, Okla. He outfitted the root beer stand with a car-to-kitchen intercom system after discovering a similar setup at a restaurant along the Texas-Louisiana border. It didn’t take him long to realize that the stand was consistently outperforming all of his other restaurants, turning a 20 percent profit on a regular basis. (There’s always money in the root beer stand.) So, in 1953, Smith ditched the other places and focused all of his attention on the root beer business.

2. Sonic could have been called "Top Hat" instead.

"Top Hat" was the name of the root beer stand, which Smith wanted to keep when he decided to expand. Unfortunately, his lawyers discovered that the phrase had already been trademarked and advised him to come up with something else. 

3. The name "Sonic" refers to its speediness.

Lars Plougmann, Flickr // CC BY-SA 2.0

The alternative name Smith and business partner Charles Pappe came up with was directly related to the Top Hat tagline they developed to promote the quick ordering process made possible by the intercom system. That slogan? “Service at the Speed of Sound.” The first drive-in officially dubbed Sonic opened in Stillwater, Okla. in 1959.

4. The first franchise agreement included an unusual stipulation.

Instead of charging a flat fee, Sonic’s first formal franchise agreement gave Smith and Pappe a penny for every logo-stamped paper hamburger bag that was used.

5. Sonic and Dr Pepper team up to host an annual carhop competition.

The winner receives $1,000 and an all-expense-paid trip to the annual Sonic National Convention. They’re accepting submissions now, so if you’re a Sonic carhop, get on it. Here’s what you’ll be up against:

6. Cherry Limeades are one of Sonic’s best-selling products.

A photo posted by Sonic Drive-In (@sonicdrivein) on

In one year, Sonic sells enough of the delicious drinks to fill more than 50 Olympic sized swimming pools.

7. Frankie Avalon was once the company spokesman.

Playing to their nostalgic image, Sonic recruited former teen idol Frankie Avalon as their spokesperson in the late ‘80s and early ‘90s.

These days, the company has turned to Oklahoma City Thunder player Kevin Durant for celebrity endorsement—specifically, to push their new line of slushes studded with candy pieces.

8. The company says it offers 168,894 drink combinations.

A photo posted by Sonic Drive-In (@sonicdrivein) on

If Durant gets tired of adding Jolly Ranchers and Nerds to his drinks, he has plenty of other options available. In fact, even though Sonic advertises 168,894 combos, the Wall Street Journal found even more—688,133.

9. Some of the best flavor combos are employee-submitted.

Rakka, Flickr // CC BY-NC-ND 2.0

In 2011, Sonic corporate asked employees to concoct and submit drink combinations and names that weren’t officially on the menu. They received more than 600 entries, from Blue Hawaiian (Sprite with blue coconut flavoring and real pineapple) to Strawberry Shortcake (Sprite with vanilla flavoring, sweet cream, and real strawberries).

10. The Sonic headquarters in Oklahoma City features a test kitchen.

Wikimedia Commons // Public Domain

The 10-person test kitchen works to invent new menu items and perfect old ones. The test kitchen staff also runs the employee cafeteria. "We want the employees to try the food and be ambassadors for the food," Chef Claes Petersson has said.

11. You can get beer at Sonic Beach.

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If you live in Florida, you may have come across Sonic Beach. Intended to "capture the South Florida essence," Sonic Beach has a patio area, 60” LED flat screen TVs, a sand beach area—and alcohol. They're the only Sonic locations that offer beer, wine, and even Dom Perignon.

12. Some Sonic locations offer adult playgrounds.

If you’re not near a Sonic Beach, don’t worry—there’s probably still some fun to be had at your local restaurant. In hopes of providing the adult equivalent of a ball pit, many Sonics offer batting cages, volleyball courts, playgrounds, and more.

13. The two deadpan men in the Sonic commercials are actually improv actors and writers.

Peter Grosz wrote for The Colbert Report for three years and currently writes for Late Night with Seth Meyers. T.J. Jagodowski is a Second City alum who has had roles in the movies Stranger Than Fiction, Oz the Great and Powerful, and Get Hard.

14. No Sonic in your area yet? There probably will be.

Bob B. Brown, Flickr // CC BY-SA 2.0

In 2014, the company announced plans to add 1,000 restaurants in the next 10 years, including an additional 300 in California alone.

This piece was corrected to reflect that Sonic's Oklahoma City headquarters has a test kitchen and employee cafeteria, not a drive-in restaurant.