You see, in Adventure Mode (akin to a traditional Roguelike in your created DF world, rather than the Colony Sim that is Fortress mode) you can create a character out of whole cloth that gets plopped into the world, or take over an extant character created through world generation. Either way, both characters are fully initialized within the systems of the game, having their own personalities, likes, dislikes, quirks, moral codes, emotional trauma thresholds, etc.
Well, one player noticed over a few runs that their character's eyes were coated with tears. Odd, they thought, so they posted on the Bay12 forums about it. After some investigation, Toady confirmed that the full personality system was still running in the background, and the character was effectively possessed by an out-of-context demon, the player. The character's consciousness was stuck watching utterly helpless as their body did all manner of unspeakable acts (assuming the player was acting as a typical murder-hobo) that conflicted with their innate personalities, were horrified at what they saw, and could do nothing but cry about it.
It's absolutely insane, equal parts disturbing and chilling and, as far as I am aware, an outcome totally unique to Dwarf Fortress created by the ridiculous depth and detail of the interwoven systems.
