Here are the plans for the original Shake Shack scribbled on a napkin

Shake Shack started out as a hot dog cart in New York City's Madison Square Park.

Three years into serving hot dogs, restaurateur and Shake Shack founder Danny Meyer came up with an idea to turn the cart into a permanent burger stand, and he sketched the plan onto the back of a napkin.

That sketch laid the blueprint for Shake Shack's original location in Madison Square Park. Ten years later, the burger chain is now a billion-dollar business with more than 60 locations across the US.

Here's the napkin that started it all, courtesy of Shake Shack:

Shake Shack

Shake Shack

Shake Shack CEO Randy Garutti explained the story behind the napkin sketch to Forbes earlier this year. Here's what he said:

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