This one is my favourite: A novice was trying to fix a broken Lisp machine by turning the power off and on. Knight, seeing what the student was doing,

This one is my favourite: A novice was trying to fix a broken Lisp machine by turning the power off and on. Knight, seeing what the student was doing, spoke sternly: "You cannot fix a machine by just power-cycling it with no understanding of what is going wrong." Knight turned the machine off and on. The machine worked. It's often not this dramatic but I see this happen all the time, when someone doesn't know the source of a problem and tries to solve it by brute force (with C, it's usually "adding and removing * and & until it works") when stopping to understand what's going wrong would have lead them to the issue directly.