These critters are a large part of the diet of many gamefish, and the Bouncer style is a great way to imitate them with flies that are snag-resistant and can bounce along the bottom making noise. Bass are well-known for liking crayfish, but large trout are also avid eaters (I recently caught a large rainbow whose stomach disgorged six large crayfish but he still grabbed my crayBouncer). Some of the examples shown in the photos below illustrate new techniques that are also useful for other patterns.
Some interesting techniques used in these example include: 1) reverse tie-in of materials to get movement of body parts as the fly comes to rest after a strip, 2) "wrapalong" style of fur strips and legs, in which one end of the material is tied in at the eye of the hook, the free end is pulled back along the shank, looped under the tail assembly and pulled forward to be tied in at the eye, 3) carapaces made of furry foam and false fingernails, with legs added after the fly is tied off using the needle technique, 4) side-tufts, which give bulk and the illusion of lots of legs, and which aid the fly in gliding in an even, hookpoint-up trajectory. (See link to detailed notes and tying instructions for the Spawning ShrimpBouncer)
(Click on the image to enlarge and to bring up notes)