I wouldn't call it shenanigans with restaurant stocks. What's happening is that they're coming back ... strong. Sure, I think some restaurant stocks are frothy right now, especially those that don't have much more room for expansion. With CMG and PNRA, however, what you're seeing is "forward" pricing on the stocks in anticipation of future earnings and cash flow streams. That is normal stock behavior and results in lofty P/E ratios. Yep, you have a mo-mo (momentum) stock right now, so enjoy the ride.
All of that said, at some point the ride will come to a complete stop. At that point, just get off. My crystal ball tends to be cloudy at times, but looking at the past history of this stock, and applying a $6/share earnings per year rate within the next 18 months, this stock has a solid shot of hitting $200. In the meantime, sit back, put your seat belt on, please keep your arms and legs inside the ride at all times, and enjoy the ride.