User blog comment:CurePikachu/Jikochuu/@comment-246574-20130211012849

I had a theory (which is now reflected on the page) that these monsters are basically well. Take the form of what the original selfish thought was. Like with the crabs, someone on lj said that "横入り" or cut-in-line, one meaning of it can be crab..so that's where that came from. (Proly untranslateable pun)

So I assume future jikochuus will follow that rule. Basically they'll be the form of what the selfish thought was before the heart was removed.