This comic made me wish that I had teachers like Mr.Munroe - with a wicked sense of humor. In grad school, Analysis of Algorithms was considered a very hard subject - and I took the class in my very first semester. It was a lot of fun, but the professor who taught the class the following semester made me wish that I had waited to take the class with him. For the final exam, he set a question paper that was an overnight-exam. Students came into the exam room at 6pm, and the invigilators (including the professor) remained there until 6am the following morning.
There were only about 5-6 questions to solve, but it took many students severals hours to solve the whole exam. I sure would have loved to be in that class - because I could always solve the problems, but not always quickly enough (I still got an A, so in retrospect it wouldn't have mattered, but I could have recounted that exam as my adventure today - but now I can't )
I don't think he was allowed to repeat the 12h final exam again