An assignment for an exam was to make a simple library management program in pascal (cataloging books, leading, receiving them back etc.), mainly to test our understanding of pointers.
Even if we also had Macs at the university, we've been asked to make a command line app. But, since I was studying the Mac OS gui programming by myself, I made a graphical application instead.
The assistant professor that was evaluatings our assignment didn't believe that I had made it myself. She probably couldn't understand it herself (but, obviously, all the relevant functions were separated from the gui code). So she asked me to rewrite everything from scratch as a command line application in a couple of hours in front of her.
I managed to do it but I was really really pissed off. Shortly thereafter I started working and dropped out.