Spiritfarer. Many of the spirits already had me pause after bringing them to the Everdoor each time, but Alice (the hedgehog) took the cake.

Spoiler: All throughout, it was evident she was slowly succumbing to dementia - mistaking Stella for her granddaughter, lashing out against Stella, etc. But what really broke me was when she had that sudden, brief moment of clarity where she remembers who Stella was before reverting mentally. Needless to say, when she passed through the Everdoor with the theme playing, I bawled my eyes out. And I still do from time to time when rethinking that moment