I happened to attend the retirement party for the Dean of the Faculty of Business at my alma mater, and he recounted the story of the hardest term of teaching he ever had, in his early days at the institution.

At 11:30-12:20, he taught a course on advertising. At 12:30-13:20, he taught a course on business ethics. Every time a student asked a question, he had to stop and remember which course he was teaching before he answered!