I never heard of the fries much less HopCat. A search showed me why. The closest location is not open yet in Royal Oak, Michigan. And to get there is 731 miles and goes through Canada. The farthest is Lincoln Nebraska at 1495 miles.......
They are expanding, so cross your fingers. Every one of them I have visited has been great - good food, good service, and awesome beer selection. I have been to HopCat in Grand Rapids, MI (KBS week-woot!); Indianapolis,IN; and the one in Louisville, KY.
I think the seasoning is salt, sugar, cracked pepper, and either dill or some malt vinegar. I definitely pick up a 'pickle-esque' flavor, especially on the untopped fries.