Hamster in a Nightshirt (1988)

Who knows how it happened that Kája Berka forgot to take his pajamas with him to visit his grandfather and grandmother in Rosebach. His great-grandmother willingly lent him her great-grandfather's nightgown, who was said to have been a ridiculous dreamer and inventor of nonsensical objects. Only my great-grandmother considered her late husband, a professor at the local high school, to be an unacknowledged genius. Kája, after sleeping through the night in his great-grandfather's nightgown, gave his grandmother the full benefit of the doubt. Not only did he experience a trip to prehistoric times in his great-grandfather's class, but he learned an important piece of information here. His older brother Radim, a designer for a large automobile company, had long been struggling with a groundbreaking invention. His great-grandfather tells Kája that he himself once worked on a similar invention, a car that would run for free and without harmful emissions, and buried the important documentation in the garden.