These came from one of my spur-of-the-moment builds. (Sometimes I'll just be fiddling with my Lego pieces when I suddenly get a small burst of inspiration and the model seems to form itself.)
The red one was built first. The shell isn't perfect, but with my supply of system pieces, it was the best I could do. I think part of my inspiration may have come from Tuggles. A popular MOC made by a member of BZPower named Authraw. (Who likes hermit crabs, by the way.)
After making the first one, however, I just had to make more. My favorite picture is the group picture at the top featuring a bunch of happy kenko crabs. :)