In the late 80's, two of my fellow C programmers and I thought that we might want to embed a copyright string into all of our executable programs that comprised a system that we were building. These were 16-bit MS-DOS programs. It seemed like an innocuous idea.

Each C program in our system included a header file with a few globals that looked something like this:

    char *dave="Copyright ... blah, blah";
    char *bob="More magic and mirth from the mavericks in MicroDev";
    char *jim="CAPS Sucks!";

The system we were replacing was written in a proprietary programming language called CAPS that was a royal pain to work with.

A decade or so later, after we had moved on to other projects and other companies, one of the old users called me. They were using the system to board a customer and in the printed paperwork that the system generated the words "CAPS Sucks!" showed up! They caught the error before sending the paperwork to the new customer, manually correcting it.

I talked with a new programmer overseeing the system. They eventually found the bug in some code they'd added that caused a pointer to go astray which ended up pointing to constants in early portions of memory ( early because those three strings were in the first #include file in the set.) Why it skipped over the first two strings, I'll never know for sure.