What's worse: The fact that Britney Spears can't enjoy a quiet drive-through experience at Carl's Jr., or that shareholders of Carl's Jr.'s parent company can't enjoy a quiet drive-through investment?

Shares of CKE Restaurants (NYSE:CKR) slumped this morning after the burger-flipping giant behind Hardee's and Carl's Jr. delivered undercooked financials.

CKE posted a profit of $0.13 a share from continuing operations during the third quarter, below the $0.16 per share it earned a year earlier. Revenue dipped slightly to $351.6 million.

The results actually were pretty much in line with what Wall Street expected. A time of challenge for the company, it's handing over company-owned units to franchisees, leading to top-line declines. Overhead was also stubborn, as pesky food costs, store remodeling efforts, and new point-of-sale system installations ate into operating margins like a hungry patron digs into a Carl's Jr. Six Dollar Burger.

Comps held up well for the 12-week period that ended on Nov. 5, 2007. Same-store sales inched 0.7% higher at Carl's Jr. and climbed by 2.7% at Hardee's. That may pale in comparison to some of the beefier comps posted lately by burger giants McDonald's (NYSE:MCD) and Burger King (NYSE:BKC), but at least CKE's same-unit sales are pointing in the right direction.

It's good to see CKE riding the burger wave adequately because that's all it's got right now. It sold its La Salsa quick-service Mexican chain over the summer. Just like Wendy's (NYSE:WEN) when it said "no mas" to its Baja Fresh concept, the burger giants have struggled with fresh Mex chains. The only one winning the battle there now is Jack in the Box (NYSE:JBX) with Qdoba. One can argue that Chipotle Mexican Grill's (NYSE:CMG) success is tied to its time as a McDonald's subsidiary -- but the company has spread its wings nicely since its spinoff.

So as the burger goes, so will CKE now. Then again, we shouldn't ignore its leveraged balance sheet. The company has been buying back shares aggressively. It repurchased 4.8 million during the past quarter alone. The tab is steep, though. During the quarter, the company's interest expense more than doubled to $7.7 million.

So keep an eye on that debt, just as you watch to see whether the company can get its operating margins back in line without sacrificing store-level growth. It's not an easy thing to keep an eye on, with or without Britney Spears circling around the drive-through window.   

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Chipotle was recommended in Motley Fool Hidden Gems (the "B" shares) and Rule Breakers earlier this year. It has more than doubled in both cases. Which stock research service is the right one for you? Find out with a free, 30-day trial subscription offer.

Longtime Fool contributor Rick Munarriz is always up for a good burger even though he doesn't live near a Hardee's or a Carl's Jr. He does not own shares in any company mentioned in this story. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy that can make you one with everything.