I don't even know what the chances of this are. I expelled a dwarf from a fortress I retired, because he went insane, years (IGT) before I abandoned. He was a necromancer doctor when he first showed up, so naturally I made him the captain of a squad for classic dwarfy !!fun!!. I then named him after a friend of mine, who we'll call Berry. When we first came under siege, the invading force of goblins was maybe thirty strong. Naturally, I closed the main entrance to my fortress and opened the trap halls, and the traps killed enough to break the siege and generally traumatize them, preventing the goblins from attempting to invade for a few years. The army continued to train in their absence, and Berry eventually became a legendary axedwarf/competent armor user.
The next time they showed up, their army consisted of a throng of fifty-or-so green skins, along with ten trolls and maybe five beak dogs. The first thing I did, naturally, was pull the lever that opened the gates to my hall full of traps and then close the main (golden) gate to my fortress. The first goblins through the traps were diced into tiny pieces, pulped by massive boulders, and filled full of holes by spiky copper balls. There's only so much a good laid trap can do, however, and they were all jammed or destroyed by the trolls after thirty or so died. So they began the twisty trek from one end of the long maze to the other, where my entire forty-strong army was stationed. They saw them through the fortifications I had carved into the walls after the first siege, so my two marksdwarves were already taking potshots at the foul sons-of-clowns. The first unfortunate goblin through the door was rushed by my military, who had been training for the better part of two years now, so he was made into a thick soup by my hammerdwarves. Afterwards, my dwarves rushed out of the door to try to stymie the army before they could set foot in the hallowed halls of Armok. Eventually, though, they pushed my squadrons from the door and stepped inside the barracks.
Then the real fun began. Pieces, severed from their rightful owners, flew off in an arc and blood was splattering everywhere. I didn't realize that I hadn't activated my 'oh shit get inside' burrow, however, so some poor peasant walked up the stairs with a bar of ☼Skunk Soap☼ and I only realized after I saw 'Urist McUnfortunateSoaper cancels Clean: Interrupted by a beak dog' and then panicked to raise an alert. Berry, who had been at the other end of the room in the beginning, finally charged into the fray and cut off limbs left and right.
Which immediately raised, being in the LoS of Berry, the necromancer militia captain. Then, when they dropped some more of the goblins, the siege was broken and the green-skins and bluebloods put their tail between their legs and left. But the fight kept going on, because Berry would kill something... and then immediately raise it. The military eventually got kill-lists in the numbers of fifty or more, only because this fucking necromancer couldn't keep his eyes shut. It was good training, but when they pulped the corpses with the -Copper Warhammers- they were wielding or we got lucky enough to raise them as friendly shambling ghouls, Berry started to stumble around obliviously pretty regularly, which sucked. It eventually made me realize that if I kept him in the military, this axelord might decapitate a farmer and then raise it as a shambling ghoul, which would eventually make my fortress into a necromancer's tower without the slabs. So I put him in the library as a scholar, so he could ponder things to his drunken, traumatized heart's content.
I thought being a scholar would be a relatively stress-free experience, but because it was under the hospital, it must have worn on him to see all the invalids who were hurt in subsequent sieges/attacks from the local megafauna/unwanted awful beasts spreading their syndrome-inducing powder, so he continued stumbling obliviously every once in a while. Maybe twice a season, I'd get a message that he'd cancel whatever he was doing to go insane for a while. Okay, whatever, he was making a steady supply of quires on math, which is funny because my friend is absolutely awful at math. The first thing he wrote about was division, producing a quire he entitled 'The Prime Divisors'. It was the first book produced in the first fortress I'd ever had setup to make paper, so I was moderately proud of it as some kind of cosmic punchline that six months after he divided a few goblins into tiny remainders he wrote about balancing long division.
Unfortunately, though, he eventually slipped into a deep depression he never recovered from. After that, I expelled him from the fortress, which I had never done before. He didn't immediately leave. Berry stumbled around the fortress for a few seasons, that magenta '@' symbol was really easy to pick out, but after a while I didn't see him anymore. I chalked this up to him leaving the fortress, his broken mind wagering he could survive in the wilderness. It makes sense, I suppose, being that necromancers aren't very vulnerable to much. No, though, it wasn't that. Scrolling through z-levels to get to my magma forges on the first cavern layer, I saw something pink in the top left. Berry had fallen down the well, which was only full of ~4/7 water. He seemed content to stay in there, and my friend I'd named him after found it pretty damn funny, so I let him stay in there. I was afraid of Berry drowning, though, so I eventually mounted a rescue mission. I dug out a secondary reservoir for the well and then drained the actual well into it, with nice dwarfy machinery. I broke him out of the chamber that previously held the water, and then transported all the water back. Then he seemed to have left, after stumbling around for a while, but no. He fell back in.
I assumed that since Berry liked the inside of the well so much, he'd be content to stay there for a long time. That was fine with me, it wasn't impacting the water quality of the hospital, and he just stayed stationary because he'd nowhere to go and he broke his foot. Eventually, though, I thought it would be a good idea to get him out of the fortress for real this time, so I drained the well once more and Berry finally left.
I thought I had seen the last of that fucker.
I started a new fortress after a tantrum spiral left half of my dwarves invalid in the floor of my tavern, covered in blood, and a larger amount of visitors and other dwarves dead. The FPS had recovered, but I doubt my dwarves would've. The normal embark was going well, I decided I'd make the most of the remainder of summer and fall to start the textile industry with pigtails. So I set all of my workshops up, and had the bright idea to make a bunch of marble blocks for a nice castle structure to protect my depot and main entrance. The first migrant wave came, and brought with it more miners, another farmer, and some nice-but-generally useless craftsdwarves (seriously, we had no bones and a bonecarver came. Weird.). Then I found some rope reed by the stream in the top-right of the map, so I set about making a farm for those as well. I read on the wiki that if you expose subterranean tiles to sunlight, they're permanently marked as 'outside', so you can make dwarves farm outdoor crops inside. I thought that was neat, so I poked a hole through the layer above my farms and plugged it up with some of our marble blocks. As we were moving all of the wood to the indoor quantum stockpiles, another migrant wave came. It happened relatively quickly IRL, but I had been AFK making some food, so who's to say.
I came back and the game was paused for the migrant wave. I unpaused and went back to the main meeting hall, waiting for the dwarves to get closer before I checked the unit list for all of the new arrivals. When I did, I saw him. Berry was back, and he's just as insane as ever. I'm thinking I build a really big well for him this time, something like 100 z-levels, right into magma, and see how long it takes him to fall down.