What Is the Matter with Willi? (1970)

Tax collectors Willi Winzig and Felix Klein are determined to stay bachelors even though their housekeeper Frau Stirnima fancies Willi and Herr Klein has fallen for their combined secretary, Frau Engel. Both of them try to keep Willi's niece Helga out of trouble when she comes to stay, unaware that Stella is only there to be closer to her boyfriend, singer Frank. When Willi gets in trouble after being too lenient with his clients, he tries to get out of it by pretending to have lost his mind.