He tends to the planet and, after a few days' time, there are three moons orbiting it and life is springs forth. He takes the gem back home, plants it in a pot, and soon a tiny planet emerges. While taking a cartload of very large turnips to market, he meets a pair of characters who offer to trade a gem for his produce.
The story was written by Naohisa Inoue, the person who created the fantastical world seen in another Ghibli film, 'Whisper of the Heart.' It is about a boy named Nona, a city dweller who is presently living in the countryside with a mysterious woman named Nigna. Unfortunately, unless you visit the Ghibli Museum in Mitaka in Western Tokyo, you will not be able to see it on the screen-or on a video-any time in the foreseeable future. 'Hoshi wo Katta Hi' is one of the finest short animated films ever made.
If it's a stretch to say this film alone is worth the price of a ticket to Japan, it's not a long stretch.