Image source: Shake Shack.

There's more than burgers being flipped at Shake Shack (NYSE:SHAK). Shares of the "better burger" restaurant operator moved lower after posting quarterly results following Wednesday's market close. The stock had rallied after posting its first-quarter financials three months earlier. 

Shake Shack is still growing at a heady clip. Revenue clocked in at $66.5 million, 37% ahead of the prior year's showing. Comps climbed 4.5% during the period -- in line with its guidance of 4% to 5% guidance for all of 2016 -- but, naturally, it's expansion that's fueling most of the top-line move. Shake Shack has seen its restaurant count grow from 71 to 95 over the past year.

Shake Shack's comps growth has been decelerating, but when you consider the 12.9% uptick in comps it posted during last year's second quarter, it's pretty impressive. It means that the average established eatery is ringing up nearly 18% more than it was two years ago.

Its adjusted EBITDA and restaurant-level operating profit grew faster. Net income has tripled to $3.3 million. That breaks out to $0.14 a share, nearly double the $0.08-a-share profit it posted a year ago. The discrepancy between net income and earnings-per-share growth is that the share count has exploded as a result of last year's IPO, but not the subsequent secondary offering since it was not dilutive.

On the menu

There's more to Shake Shack than beefy burgers these days. The Chick'n Shack fried chicken sandwich that it introduced earlier this year is a hit. It is now the third most popular item on the menu, accounting for 8.4% of the sales that the chain rang up in the second quarter. 

It's not the only new item on the menu that's taking off. The Bacon Cheddar Shack that it rolled out in June has become the chain's most successful limited-time offer. Unlike the Chick'n Shack, which is a permanent fixture on the menu, Shake Shack's offering specialty burgers that will change every few months. 

Wall Street didn't like the report. Disappointing comps and the stock's lofty valuation weighed on Shake Shack stock. It didn't seem to matter that it landed just ahead of analyst profit targets, something it has done consistently since going public at $21 early last year. 

The boobirds are even shaking off the burger chain, once again raising its outlook. It now sees $253 million to $256 million in revenue, up from its range of $245 million to $249 million issued three months earlier. It now expects to open 18 domestic company-operated eateries, two more than it was forecasting to roll out in May, and five more than it was targeting back in February. 

Shake Shack stock has been a success for those who got in at the IPO, but retail investors haven't been as lucky. Shake Shack may have gone public at $21, but the stock opened at $47 on its first day of trading -- higher than where it sits now. There is more going right than wrong at Shake Shack, but it's hard to impress Wall Street when your trailing earnings multiple is in the triple digits.

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