I have caught crappie on flies ranging from size 18 dries and nymphs to size 2 Dahlberg Divers and 5 inch long Lefty's Deceivers. We have some big crappie around here. Plenty of small ones too. It seems they will try to eat almost anything when in the mood. Most of the time when intentionally targeting crappieI use simple flies tied on Wapsi 1/80th oz fly rod jigs like iaflyfishing posted. No more than two materials usually. Marabou tail and a body made from chenille, come type of shiny braid, peacock herl, ostrich herl, or some type of dubbing spun in a dubbing loop. I carry these jig flies in a selection of colors and shades ranging from all black, to all pearl flash material, including browns, olives, reds, and yellows.

Topwater crappie are a lot of fun if you can find a situation where that works. That happens in the summer here on some lakes when crappie start chasing schools of bluegill or bass fry or shad. A small crease fly or Gartside Gurgler does the trick, as well as small pencil poppers. I tie small crease flies on Tiemco 200R hook in sizes 6 through 10. I don't even bother to color them or coat them with epoxy. Just white foam and a sparse craft fur tail.

I have also caught crappie on bluegill size poppers and foam bugs around weed beds.

We have 2+lb crappie in some of our local lakes with some around the 4lb mark and they eat big flies I'm casting for bass but I don't target crappie with big flies intentionally.