Dwarf Fortress is a game bestowed with a bounty of curiosities. From watertight cat bone floodgates to gargantuan demonic monstrosities being hauled by a single dwarf, this game has baffled minds both dull and brilliant alike. Today, however, it ends. Today, I come before you to present an end to the confusion. Today... I explain.
You see, Dwarf Fortress is set in a 4-dimensional universe.
1. On Dragons
That's right, 4-dimensional. The reason this is confusing is that the game is actually played in 3 dimensions. The world, with its ramps and its caves and its eyeball grass and its mountains, is entirely 3-dimensional. You dig in 3D, you build in 3D, you stab, ignite, throw, talk, and swim in 3D.
However...
That dragon that you just let into your fortress by accident. How did it fit? Aren't dragons meant to be incomprehensibly vast? How does it manage to chase your miner down a tiny access shaft like that? The answer is that the dragon is, in fact, 4-dimensional. What you see in your tunnels is the infinitesimally small part of it that manifests itself in 3D.
It's not just dragons though. The dwarf it's chasing is also 4D. So is the XCave Spider Silk LoinclothX he's wearing, the tree he was on his way to cut down several seconds before, and the door that was just set on fire and smashed to pieces. In fact, every creature and item in the game is 4D. All you ever see of them are their 3D manifestations, which are never larger than a single tile in-game.
The upshot of this is that, when you see a dragon on your screen, you're looking at the 2-dimensional representation of the 3-dimensional manifestation of a vast 4-dimensional creature.
2. Quantum stockpiles and Prone Villagers
A 4D object protrudes into the 3D world by a variable amount. If it is the only object in an in-game tile, it is free to protrude as much as it likes and take up as much space in the world as it likes, as long as it doesn't exceed its game tile. If another object's 3D manifestation is put into the tile, the object may be forced to recede into 4D space a little to make room for it.
An example of this is when a single human can completely block your passage as an adventurer, but is able to recede enough to let you pass if you lie down (and therefore take up less than a complete tile of space). It's also why chunks of microcline are both small enough to be piled up in the thousands without overflowing a single tile, and large enough to make a watertight wall across an entire passageway.
3. XXTroll Fur LoinclothsXX
In Dwarf Fortress, items can take damage and gradually accumulate wear over time. To the player, this appears to be a simple progression, wherein the item is damaged and eventually destroyed entirely, leaving no trace.
In fact, what is happening is that the item is losing its foothold in the 3D realm. As it is 'damaged', it is instead slowly pushed back into 4D space until eventually it has entirely left the 3D world and can no-longer be observed from within it.
4. "You latch on firmly!"
It has been observed that, during combat, it is possible for creatures to grasp any part of another creature's body using any of its own body parts, resulting in amusing situations such as when a dwarf may have hold of a leg with his arm and an ear with his hand, while biting onto any number of other body parts with numerous individual teeth.
The reason this is possible is that creatures in Dwarf Fortress are not constrained by the 3-dimensional physics we're used to. There's no reason why a 4-dimensional kitten can't let its back tooth bite onto a goblin's face while its other teeth all take shortcuts through 4D space to maul toes, guts or any other body part that it takes a liking to.
5. Teleporting Vermin
In-game, small creatures such as rats and flies appear to blink in and out of existence. This is in fact a trait unique to small vermin, which will wander in and out of the 3D world aimlessly, appearing to teleport several metres at a time as they move around in 4D space.
6. One final curiosity
When objects' manifestations are pushed around by the flow of water (which, it should be noted, is entirely 3-dimensional), they sometimes seem to disappear. This is because they have been temporarily pushed out of the 3D world. Dwarves, with their 4-dimensional hands, can still pick them up out of 4D space, but they're invisible to the 3D simulation until this happens.
Note that, due to some quirk of fluid dynamics, items can sometimes be pulled back into 3D existence by the flow of water as well.
...that's about it. Hopefully this all makes sense, and I'll be more than happy to enlighten readers on any points that seem fanciful or inconsistent.