Plushie furries
is the plushie the outer layer
or the polyfill
what is the animated part
unstuffed living plushies, still sentient? Waiting to be filled up?
stitchy
For Echo, its animated part is probably the incorporeal soul inhabitting the plushie. But then again, it does sometimes identify as the plushie itself, implying that the plushie experiences continued existence even in the absence of the spirit. Now what part of that is the essential part, I could not even begin to answer.
Regarding rhe spirit/vessel stuff, probably both interpretations are true. Fae are masters at holding contradictory truths.