Hair jigs are very popular for catching crappie, especially in colder water. I think this has a lot to do with plastic can become rigid and not move as much in colder water. You can pulse or stutter a hair jig on the fall and it will open up and sort of “breathe” in the water. It just looks alive casted and pulsed, tight lined or even vertical fished in the winter.
A standard maribou jig has caught a lot of crappie, but there are a lot of other good hair and feather jig options out now. Some really creative stuff out there and some really good stuff coming this year from what I hear. I have had luck as well with jigs designed to catch fish on the float and fly technique.