For instance in one game a dragon attacked my fort. NBD. Everyone got inside and I was planning to catch it in a cage trap. Then use it as a decoration.
However there was a group of Human traders at my Trade Depot. They decided to run over and fight the dragon. Now the dragon is running around breathing fire. Which started a forest fire. Which destroyed my wooden bridges and doors.
Completely unscripted fun, just a result of the game simulation.
Also the game manages to make you hate goblins and elves through your interactions with them.
In evil regions eyeballs grow out of the ground, blinking at passing dwarves. However cattle will happily graze on them.
If you "delve too greedily and too deep" you'll unleash horrors of the underworld.
There's just a lot of neat stuff there.