Well... My current fortress is giving me a lot of those moments.
I remember when, making a waterfall to fill an underground pond from a brook, one mason decided it would be cool to stay in the tube where the water was going to flow. Predictable result, he falls 3z-levels and get badly injured. But then he decides to do the most logic thing: start drinking water, standing below the waterfall, while he is being surrounded slowly with 6-7 water. Awesome.
From this same waterfall, I turn it on (after rage-savescumming), and then.. SIEGE! I forget completely and closewatched my militia fighting them, until an ogre gets to my living quarters, which, to my surprise, are in 1-2 water. the damn waterfall. It got more hilarious when, after finishing that ogre, i looked in the pond, only to see three civilians drowning, and a LOT of water passing through the ¿sealed? doors.
And, speaking about my militia, my current best soldiers all share a strange love for slowly dismembering their opponents, until they're only torsos with heads.. and then leaving them for dying of blood loss. Seriously, they just stand there for several "cliks" until they die, just staring at them...pretty funny when you get ambushed and several moments later the only things that are left are several quadruple amputees goblins just somehow crawling to their salvation