It's always fun discovering bugs in your code that make you wonder, 'How did this ever work?' It's like going on a road trip, and noticing a funny chunka-chunka-chunka noise your car makes whenever you take it over 65mph. You get home, and you take it to the mechanic and they open the hood and say, 'Oh, well, here's your problem. The engine's been replaced by a wedge of cheese.'

On the one hand, it's comforting that the solution is so simple. On the other hand, it raises a troubling question: 'How the frack did I drive 450 miles in a cheese-powered car?" It takes a while to regain one's trust in the idea of a predictable universe.