The Cat Returns

The Cat Returns is something of a loose spin-off of "Whisper of the Heart" as it features two characters from that film: Muta (the cat from "Whisper") and the Baron (the cat statue from "Whisper"). There is no other connection between the two movies and this is not a sequel. The story is based on Neko no Danshaku (Baron of Cat) by Hiiragi Aoi.