While learning there are different types of clouds of varying densities, Nobita wondered if there was one big enough for Heaven to exist on. Naturally the entire class laughs at him including Suneo and Jaian so he decides to ask Doraemon for help. Since kingdoms in the clouds only exist in folklore and fairytales, they decide to make their own kingdom amongst the clouds.
As they enjoy their newly built kingdom in the sky, their cloud island is carried by the air currents and crashes into the peak of a mountain. There, they discover a unconscious young man and an animal that was thought to be extinct. Before long, they even meet the "Sky Dweller" Paruparu and her people. However, it seems there is a secret she won't let them know as they do their best to keep them in the city.
I think this is the first time I've seen a broken Doraemon.
Hoi from the tiny "Donjara Villagers" joins in midway, which is a comic episode drawn around the same time as the Underworld movie in 1984 apparently, as part of the "Green Doraemon" campaign. The cocoon style sleeping bag gadget was also first featured in the episode before appearing in Animal Planet. The idea of tiny entities was then re-used for the Little Star Wars comic and movie afterwards.
Pretty good movie overall and rare to see it link to past episodes from the comic or animation series including a certain tree that didn't get its own movie until after 2000.