Jeff Flug, President of Union Square Hospitality Group; Danny Meyer, Founder & CEO of Union Square Hospitality Group; and Randy Garutti, Shake Shack CEO, fourth left to right, celebrate as they ring the New York Stock Exchange opening bell, Friday, Jan. 30, 2015. Shares of Shake Shack Inc. have more than doubled minutes after they debuted on the stock market Friday.(AP Photo/Richard Drew)