Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Sonic (Nasdaq: SONC) surged as much as 14% in intraday trading today after the company issued a press release foreshadowing surprisingly strong revenue trends.

So what: Management said same-store sales -- sales from stores open at least a year -- for the fiscal third quarter, ending next month, are now forecast to come in between 4% and 6%. Comps improved just 1.2% in fiscal Q2.

Now what: Even so, this classic burger builder is on a roll. (Yep, pun intended.) Sonic easily beat estimates in its fiscal first quarter -- and that's when comps were still declining.

Should investors take a bite of the stock? I don't see why not. Sonic trades for a small premium to the five-year earnings growth analysts estimate, resulting in a perfectly reasonable 1.23 PEG ratio. By contrast, McDonald's (NYSE: MCD) sports a 1.47 PEG at current prices.

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This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.