Crick (creek) rat are sketchy white people who live in the outskirts of a larger city. For example, a "crick rat" living just outside of Pittsburgh, perhaps in the N.Hills. They have a Pittsburgh zip code. These people may or may not have all their teeth. Chances are they don't have a job. Chances are high they'll ask relatives for money. Note: actual proximity to a creek (crick as it's pronounced in Western Pennsylvania) is not necessary to be considered a "crick rat".
My loser cousin from Sharpsburg called to borrow money again. That "crick rat" won't feed his kids and he's behind in child support, but he's trying to buy a sports car.