Two sisters move to the country with their father in order to be closer to their hospitalized mother, and discover the surrounding trees are inhabited by Totoros, magical spirits of the forest. When the youngest runs away from home, the older sister seeks help from the spirits to find her.

This is a short film about 14 minutes long, which was shown for a limited time only at the Ghibli Museum. It tells the story of Mei and her friend the kittenbus (the child of the original catbus from My Neighbor Totoro). Mei is just small enough to ride in the kittenbus, which is only big enough to stir up dust devils, rather than making whole fields of rice sway in its breeze. One night they have an adventure in which they fly into the forest with many other cat-based vehicles, including many buses and trains. There they meet Totoro and many similar spirits, all heading for a gigantic catliner. This liner cruises off into the sky and the kittenbus takes Mei home.

[Source: AniDB]