Well I’m used to them so need to take a minute to think about what you may find interesting.
I think the coolest thing they do is that the females carry their eggs under their bellies, and the babies hatch out there.
Crayfish are also very important parts of freshwater ecosystems, they eat most things (plants, snails, tadpoles, fish eggs, leaf litter, smaller crustaceans, each other), they move the sediments around, they are eaten by larger animals such as otters and birds. And they are also declicious, esepcially in “crawfish” broils in Louisiana – I once went to a Cajun festival where boiled Red Swamp Crayfish were piled up on a table and you ate all you could. Brill!