1978 film by Radim Cvrček

Eleven-year old Mísa has the temperament of a proper boy and endless problems with the grown-ups. It is no wonder that he longs to become an adult without further delay. Mísa keeps house together with his father and has various duties. After a failed attempt at dish-washing he goes off to the research institute where his father is working on an important invention. He is trying to produce a substance that would make poultry and other animals bigger and thus help the struggle against famine in the world, but so far he has only managed to produce a shrinking substance. After his father leaves the laboratory, Mísa mixes up different ingredients and makes the growth substance. He drinks it and instantly becomes an adult. His father, conversely, turns into a toddler after drinking the shrinking substance with his beer by mistake.

Tanya, a 10-year-old Russian tourist traveling with her parents from Prague to Brno, is left behind in a foreign country. Tanya leaves her compartment when the train stops because of a cow. Disobeying her parent's instructions, she gets off the train to investigate, lingers too long, and is left behind. Cold, lonely, and clad only in her pajamas in the unfamiliar countryside, the girl is relieved to meet up with two rather nervous Czech boys camping out together for the first time. At first the would-be "cowboys" are frightened by her ghost-like appearance. After hearing her story, the boys find Tanya a dress to wear and accompany the girl on foot to her final destination, Brno.