Many things are going on in my fortress.
With the most inconveinient thing being the wereweasel incident in late winter 555, first year of my fortress. A wereweasel just showed up on the map, and quickly made it's way right into the heart of my unguarded fortress. Not that the weasel was that much of a danger itself. The captain of my guard and my dogs managed to bring it down in no time. Yet it managed to bite said soldier, which I didn't notice right at the beginning. Let's just say, the log was rather long, becasue literally every dwarf and livestock was somehow involved.
About one month later (just right after the seasonal auto-save), right in the middle of the tavern, the dwarf turned into a weasel. Not only did it manage to dodge a handful of attacks from my miners' picks and my woodcutters axe, but no, it bit 3 more dwarfes. With only one month to go, I really had a hard time trying to entomb all three of them in time.
And there, they still remain.
And, right before that, mid autumn, there was the werepanda incident. Luckily, it got resolved pretty quickly by the guards of the dwarfen caravan, without any causalties.
Well, exactly one year after that, autumn 556, I had a similar incident, but with a wereelephant this time. Let's just say, it went pretty well for me. It slaughtered pretty much the whole caravan, with only one survivor, who bled to death shortly after. Pretty well for me because I inherited not only loads of armor, but also three caravan carts worth of finest stuff.
Long story short - once again I'm surprised by what damage a small creature can cause and how easily even the worst possible enemy can be fought off under the right circumstances in this game.