Wenn's donnert, blüht der Gummibaum(1982)

Some unusually intense meteorological event causes a family to suddenly swap roles. That means that the children are in charge and the adults must obey. Coincidentally, mother’s new admirer, Mr. Droehmbüdel, proposes marriage but when he enters their apartment, he is very surprised by the strange family relationships. With determination her son (Tom) tries to chase him away against constant pleas from his mother and grandmother. But Mr. Droehmbüdel does not give up and is constantly inventing new ways to gain access to his future home.