Dr Pepper is the oldest major soft drink in the U.S. According to the U.S. patent office, Dr Pepper was first served at a drugstore in Waco on December 1,1885.

Now, 125 years later, Dr Pepper sells more than 530 million cases world-wide.

The amount of Dr Pepper sold each year in Texas alone could fill Cowboys Stadium 338,000 times. And the number of cans sold each year in Texas could wrap around the earth's equator 8 and a half times.

Dave Thomas has a secret. A really, really big secret. The Senior Vice President for Research and Development at Dr Pepper Snapple in Plano is one of just three people in the world who know the 125 year old, 23 flavor formula for the original Dr Pepper.

"Can't even go there, not gonna tell you anything about the 23 flavors," said Thomas.

But he is willing to share some of the other secrets that make the Texas original and the more than 50 other brands in the Dr Pepper Snapple Group so tasty.

SECRET # 1 - REAL DOCTORS WORK AT DR PEPPER.

About 75 people work at the company's state of the art research and development lab in Plano, many of them scientists with Ph.Ds and other advanced degrees. Together they work on improving the more than 50 products already in the Dr Pepper Snapple Group, and create new ones.

SECRET # 2 - EXPERTS CALLED "FLAVORISTS" COME UP ANY NEW DRINKS, LIKE THE MOST RECENT DR PEPPER CHERRY.

"You know, there's only a couple hundred flavorists in the entire country. and here at Dr pepper, we've got four of them," said Thomas.

The Flavors Technology lab is filled with samples of more than 3,000 flavors, including the 23 in Dr Pepper.

"So what we see here are things that will give us mostly things like citrus flavors, things that go into our beverages, fruit flavors. vanillas, root beers, colas, and of course Dr Pepper," said Steven Kramer, Director, Flavor Technology.

SECRET # 3 - EVERY NEW PRODUCT STARTS IN A CHEMISTRY LAB WHERE SCIENTISTS PUT THE FORMULAS TOGETHER.

Some formulas are less secret than others. One concoction meant for ice drinks, like Slurpee's, contained kiwi, watermelon, dragon fruit.

SECRET # 4 - SOMETIMES, PEOPLE MAY BE A LITTLE BLUE TASTING DR PEPPER PRODUCTS.

Blue lights overhead in the "sensory lab" mean taste testers can't tell a new drink's true color.

"Sometimes you may have subtle color differences, and you want to take that variable out of the equation," said Thomas. "So by having a blue light, it just mutes everything so that color's not a variable. They'll sit in these cubes, a little door will open up in here and you know a tray of samples will come through, and they'll be able to answer the questionnaire, put it into the computer and we get real time data and results."

SECRET # 5 - THE BIGGEST SECRET OF ALL THE 23 FLAVOR FORMULA TO DR PEPPER.

The secret is so big its under lock and key inside a tightly secured vault hidden somewhere in the building. "We can't tell you the 23 flavors," said Thomas. "It's been a secret since 1885. You think I'm gonna tell you now?"

Some secrets are meant to stay that way, but we did learn that prunes are not one of the 23 flavors in Dr Pepper.