This crab is loco! 
https://user-images.githubusercontent.com/2152766/178117456-abdad962-1b63-4daf-a797-30d2a1a18be7.mp4
Achieved by re-parenting the crab root control to the box that’s jumping around. I got Locomotion to walk backwards using the trick from this thread here:
https://forums2.ragdolldynamics.com/t/a-question-about-locomotion/424/3