In Dwarf Fortress, fire is an undetectable but deadly disease.
Infinite energy can be obtained by using a vertical ring of dihydrogen monoxide.
Dwarves live in mortal fear of deer and hoary marmots.
With cave-ins disabled, one can create floating islands.
Dwarves are extremely greedy, gathering clothing and other equipment, usually ignoring their fallen brethren and goblins until they become late.
Geothermal power is an extremely limited resource.
Dwarves tend to be extremely environment-unfriendly, requiring many trees if they cannot find magma.
Goblins are interminable loiterers.
Merchants are known to have consumed excessive amounts of mercury.
Dragons are nothing but hot air with TEMPERATURE disabled.
One locale can have both ice and water outdoors in adjacent tiles with TEMPERATURE disabled.
Nobles flock to deathtrap fortresses.
One axle can channel infinite amounts of torsion.
A masterwork bolt is more valuable than a child.
Animals are culled so that everyone else can move faster.
Elves give wood, but they don't like to take it.
A fireproof structure can be constructed from charcoal.
The mere presence of dwarves will cause drought in some locations.
Attempting to reference bathing will return a null pointer.
If traders have extra space, they don't mind being offered trash, as long as it is your trash.
Machines can only be made from stone parts.
Conservation of energy and matter is a theory that has been disproved.
Vermin have the same properties as quantum mechanics from NetHack.
The insane are ignored.
A bin looks exactly like a set of up/down stairs.
Dwarves revel in the imagery of their dead brethren.
Historians know everything about obscure people who have accomplished nothing, and are completely mystified by fortresses that have created many artefacts and have been visited by many traders.