My wife told me about this one, which was depressing.
For me: Y2K was not only not a hoax, fixed by everybody in the field working like 80 hour work weeks, but that it is coming again in another 25 years. But now, almost nobody has been trained on these systems since the 90s and all of the people who fixed it last time either have already retired or will retire in the next 10-15 years.
I know this most intimately because my boss laughed at me because I'm gonna be left holding the bag on this when he's long gone.