Fans of Chipotle (NYSE: CMG) know the chain's trademark foil wrapping, but investors seem to be imagining gold foil around the burritos these days.

Shares of the burrito king have been on fire lately, jumping more than 20% in the past three months as the stock sets a new record high seemingly every week. The upward momentum seems to be based almost entirely on the broad market's blowout first quarter, as well as other macroeconomic factors such as the warm winter. It's often a foreboding sign when a stock jumps so much without direct cause. With the burrito chain set to report earnings today after markets close, let's take a closer look at what the last few months have brought the salsa slinger and see what investors should look for on the call.

Is this performance all-natural?
Since trading near $320 in mid-December, Chipotle's shares have climbed almost 40% on almost no news out of the company itself, other than its middling earnings report from the beginning of February. Generally, this would be a warning sign for investors. Analysts on this site and others have called for a Chipotle correction for months, if not years, and with 10% of its shares sold short and a P/E ballooning to 65, the company may have more to lose than to gain this time around. Even with a projected growth rate around 20%, shares should not be climbing as fast as they have been.

For the first quarter, analysts are calling for $631 million in revenue and $1.93 in EPS, an estimate that's moved up slightly from $1.89 three months ago and $1.91 two months ago. This figure represents more than 30% growth from its $1.46 EPS a year ago, and analysts' predictions have been generally accurate given Chipotle's straightforward business model. Investors seem to be optimistic as shares climbed 1.3% Wednesday even though the market was down.

A mild winter across much of the country likely boosted sales for the quarter, and concerns over "pink slime" may have also helped propel the stock as the company is known for serving naturally raised meat. Chipotle also unveiled its first TV ad during the Grammy Awards in February, an animated depiction of a farmer rejecting factory farming and returning to traditional methods. The ad, known as "Back to the Start," won best animated short film at this year's International ANDY Awards.

What's on the earnings menu
The Grammy ad was a bit of a surprise move for the burrito chain, which has generally avoided major media advertising. Founder and co-CEO Steve Ells will likely tout the award-winning ad on the call and may comment on any other advertising initiatives the company plans. While I thought the ad was unique and effective, I'm hoping the company will stay away from TV. Chipotle has built a strong reputation through word-of-mouth and its quality products, and straying into traditional advertising seems unnecessary at this point.

The company's ability to create brand value through other means puts it on par with other "best-in-class" brands such as lululemon athletica (Nasdaq: LULU) and Whole Foods (Nasdaq: WFM), both of which avoid the kind of commercials that are common among competitors. Like Chipotle, those two have leveraged that brand strength into wider margins and increased customer loyalty. I would also fear that an increased media presence would make Chipotle more like McDonald's (NYSE: MCD) or Coca-Cola (NYSE: KO), both of whom seem to rely on bombarding the airwaves to maintain their industry dominance. Their huge ad expenditures seem to be evidence of a weaker product, and in age where consumers are becoming increasingly wary of traditional advertising and fonder of "organic" businesses, I expect that approach to bring diminishing returns.

Chipotle's expansion is always a hot topic as well. In its last report, the company said it planned to add 155 to 165 new restaurants in 2012, and investors should also expect to hear more about the fledgling Shophouse Southeast Asian Kitchen chain and Chipotle's forays into the European market. On the last earnings call, CEO Ells said the company expected to open a second Shophouse location in Washington, D.C., this fall, and planned on adding two more Chipotle outlets in London as well as its first in Paris this year, which should be open within weeks. Any news of additional international openings or Shophouse locations should be music to investors' ears.

To stay or to go?
Earnings calls can be a nerve-racking time for investors, especially when momentum stocks like Chipotle are on the docket. The stock's huge rise in the last few months seems in need of justification, and a bottom-line miss could set shares back by at least a few percentage points. In its 2012 outlook, the company said it expected food costs to rise in the mid-single digits and same-store sales to grow by a similar percentage, both of which seem conservative. Food inflation has taken a bite out of profits in the past, and shareholders should always be ready for that specter to rear its ugly head.

But regardless of Thursday's report, it's important for investors to keep an eye on Chipotle's long-term prospects. Food costs may be an occasional concern, but without an equal competitor or a big scandal like a lawsuit or an E. coli outbreak, I see little standing in the way of its continued success. The company's products inspire legions of devotees and it continues to set the bar in areas such as sustainable agriculture, serving only naturally raised meat and more of it than any other restaurant in the country. A recent FDA missive asking meat producers to voluntarily reduce their use of antibiotics on livestock only underscores the gap between Chipotle and much of the food industry. With claims like that and plenty of open markets to penetrate, it seems like no news could very well be good news for Chipotle.

One more bite
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