As far as my understanding goes, The Cat Returns is a sort-of-sequel/spin-off to an earlier Studio Ghibli film called Whisper of the Heart, which I have yet to see but now want to.
It is a lovely little film which I think would sit well with another, though much earlier, Ghibli film My Neighbor Totoro as they are both very much family fantasy films that have wonderful stories. I loved the characters in this and recommend the Japanese voice cast with English subtitles as even though I have not heard the English cast, the originals fit very well indeed.
A great film, recommended for anime and Ghibli fans and a good introduction for children into the genre.
8/10