This was originally going to be a short straight-to-video project, but Toshio Suzuki was so impressed with Hiroyuki Morita's storyboard, and especially the main character of "Haru", that he encouraged Miyazaki to give this cinematic release.
The trivia item below may give away important plot points.
The English-language title of this movie is "The Cat Returns". There are a number of possible reasons for this title. The character of the Baron is recurrent: he originally appeared in Whisper of the Heart (1995) as a statue, but was nonetheless one of the main plot-points of the film. The title could also be a reference to Muta, the large cat who reveals himself to be "Renaldo Moon" who has returned to the cat kingdom after many years (and he also originally appeared in Whisper of the Heart). He is a notorious criminal in the Kingdom as he devoured a whole lake of fish in one session and the story of his "crime" has been written on the walls of the tower in which he reveals his true name. Another possible reason for the title is the return of the cat prince at the end of the feature, his return sets everything back to the way it should be. Among many speculations surrounding the reason for the title of "The Cat Returns" lies one that can be attributed to Yuki. Yuki, the "dirty kitten" that Haru helped as a child, has "returned" to now save Haru as Haru has saved her.