Little Ghost (Wintergreen)

Adoption. A star-being who alternately poses as a cat and a human volunteer at the local Good Samaritan's foster home. Tasked with preserving the knowledge of family lines and mothering. Possesses a (confusing to cats) significant amount of medical knowledge but the years have blurred the context; has difficulty differentiating "81 mg aspirin" from "willow bark" for example.
Thrushfur and Celery both know them: the former as her mentor's new apprentice (and secretly her own mentor themself) and the latter as one of his many foster siblings. (They/she)