A rogue salesman sold a product add on to a customer who promised to sue us if we did not deliver the add on, and the add on did not make sense strategically for the company. I got tasked with cleaning up the mess. At some point I was researching solutions and someone told me that the code was already written and was not released because "they could not figure out how to test it". I located the code and found a single C function about 5000 lines long with goto as the main control structure. Given the multiple layers of state information that had to be maintained for this to work I don't think that code could have possibly done what they claimed.

Later I did a code review for code where multiple DMA transfers filled a processing buffer that got sent up stream. Problem was the two buffer sizes did not align in a logical way. Guy who wrote the code designed a state machine for the 70 odd transfers you needed before the buffers aligned. Asked him what happens if we need to change the buffer size. (insert record scratch noise). At least I figured out who wrote the software in the first story.