I think I mentioned this is a previous thread but occasionally I get some monster crappies in (18 inches and above) and they invariably turn out to be natural hybrids. They will look like one of the two species (black or white) but have the spine count of the other. I talked to a local biologist about it and he says he sees the hybrids from time to time too.
Here's one I mounted that was 20 or 21 inches.