Well I just got one of those pieces back in the shower (that's usually where it happens). This one has been occupied for about 6 or 7 years.
There's a Babylon 5 episode in which someone gives Londo a poison. He makes a long speech about how the poison comes in two parts. Both parts are harmless alone but if you've eaten the first part ever in your life then later in life the second part will kill you. He says it's an old school way of assasinating someone. It's a wonderful metaphor and a great plot device, but I always wondered: what's the point? To Londo this is highly threatening, the guys says the second dose could be delivered at any time in his food or drink and this freaks him out. But why does this freak him out more than the same threat made about a single dose poison? Why does this poison make things more scary? I mean maybe it's because it would pass some chemical detection that detects poisons but any 26th century poison detector could be programmed to detect this substance as well, couldn't it?
Every poison detector except one. The one that is centrally relevent to Centari culture. The Centari use food tasters. If the food taster dies then the food was poisoned. If he lives then the food is safe to eat. Unless the poison comes in two doses and the food taster is only exposed to one of them!
All this time I thought that that plot device was just the writer stretching to create an interesting scenario....but really the writer was showing a keen understanding of the cultural history of the Centari imperial aristocracy.
Now that I think about this it might have been really obvious to everyone else. Like maybe they even set it up by having the revelation about the use of food tasters in the same episode. Heck maybe the antagonist even explained this and I just missed it. I don't have the episode to review, I just have the nagging memory that I was confused/annoyed by it at the time (and ever since).
Imagine the things I could use this piece of my brain for now that I have it back!