Is Shake Shack changing its menu?

Shake Shack is now worth $3 billion after quadrupling its value on Wall Street, and the line to get a burger is longer than ever. The popular chain re-opened its original location in Madison Square Park last week after it was shut down for some critical innovations, but rumors suggest bigger changes are brewing behind the scenes.

Fans and critics couldn't help but notice a patent for "Chicken Shack" was claimed, while Shake Shack restaurants are appearing in more and more cities across the U.S. with an always evolving localized menu.

Shake Shack was built as an extension of a hot dog cart in New York City, but has seen overwhelming success. Even 10 years later, patrons wait in impressively long lines on a regular basis without question. So what is it about this seemingly ordinary burger shack that is so special?

Founder Danny Meyer and CEO Randy Garutti explained on "CBS This Morning" Wednesday that they just had the right idea, at the right time, with the right experience.

"A 30-year history of fine-dining restaurants is our pedigree," Garutti said. "And when Shake Shack was born I think we caught and created the wave of people who say: 'I don't eat fast food anymore, my kids aren't going to eat that way, but I still love a great burger--and I want to know where the ingredients come from, and I wanna know that its thoughtful and I want to share the ethos of a good company.'"

Shake Shack gave them that, and is now a worldwide success.

While speculation grows about a potential chicken sandwich or a chicken-only shop in the works, Meyer and Garutti insist they don't have any announcements to make on the subject.

"We are always tinkering around in our test kitchen; we can't help ourselves but to continue to have fun thinking about new menu items," Garutti said. "Every time we make a decision about Shake Shack, each other Shake Shack has to get better in the process."

Menus do change, especially catering to local specialties. For example the Austin menu will have a Lockhart Link Burger, which is a Shack burger topped with sausage link from Kreuz Market. But regardless of what is on the menu, they will continue to work with local and artisanal ingredients.

Future expansions will include Southern California, which famously already has a wildly popular not-so-fast food burger shop, In-and-Out Burger.

But Meyer and Garutti aren't nervous; they know Shake Shack will always be able to hold its own as long as they do their job.

"Shake Shack is an experience," Garutti explains. "It's a community gathering place, people come together."