i forgot to lock the doors to the first floor of my giant cave spider silk farm, and a curious puppy just had to wonder in and so got webbed from friendly spider fire, and promptly falling 1 floor down due to the repeating retracting bridge. The puppy sustained horrible, horrible injuries due to the fall and due to all the webbing that fell on him, but now there was no way for him to get out at all since the second level's bridge is only activated by a manual lever and was another retracting bridge. So i pulled the lever so the puppy could get out from the last level, which is where my dwarves retrieved the silk. The puppy took another round of falling with all the accumulated silk on his back, one of which broke his lower spine so he started suffocating. The puppy soon died, letting out one last muffed "yelp" and his corpse made my dwarves wander into the silk collection area since they wanted to store his corpse in the refuse quantum stockpile. Now my silk operations are shut down for this time since i was doing a stockpile overhaul, and soon there was massive job cancellations, children, other pets, and items getting stuck in the collection zone due to all the webbing and dwarves getting webbed trying to get stuff from it. I ended up just forbidding everything and leaving the door open as well as making the area low traffic, so no more dwarves went inside and the children/pets slowly wandered out. But dam, it was a hell of a mess, so many items stuck in there, clothes, logs, corpses, rotting food, and the place was full of miasma, which proceeded to sink into my central stairwell due to the close proximity to the collection zone.
all because 1 puppy had to be curious...