Quite obviously crayfish, humans, and many other animals have apendages. Snails, however do not.
crayfish, worms, and snails
Freshwater crayfish and snails.
You
crayfish eat tadpoles,snails,small fish, and insects.crayfish also eat plants and waterweeds
They use their shells
Humans
Yes if the shells get broken otherwise no. I keep crayfish and Tilapia together and crushed some snails for the crayfish to eat, the Tilapia ate them before the crayfish had chance.
Puffer fish are a carnivore, and tend to be nocturnal hunters. They have to eat hard-shelled, meaty food in order to survive, including crabs, clams, snails, oysters, crayfish, cut up prawns and shrimp. They do not eat humans.
Humans
this is the answer they are both living things also that they both have external skeletons
Crayfish eat fish, shrimp, water plants, worms, insects, snails, plankton, and more. They will also eat dead plants and animals.
oysters, scallops, clams, snails, crabs, crayfish, lobsters, shrimp, krill, barnacles.