The Reference Explanation Thread

[Zeke]

Okay, here's the thing. I was just rereading my "Conscience of the King" fiver and I happened to notice this bit...

Riley: (over the comm) Bleah. Another rotten day in the life of Riley.
Sulu: Foiled again, eh?

That's just the start of the scene, but here's the point: there's some kind of pun in Sulu's line, and I can't remember what it is. It's probably a joke on "foil" as in the kind of sword, but I can't figure it out. Does anyone get it?

Anyway, the reason for the title of the thread is that this got me thinking... when you read something with references in it, you can often tell there is a reference even if you don't get it. Some of you guys must have had that experience. So this will be a thread for asking about such bits, and the author or another reader will answer you. (The long-stagnant Jokes and References page served a similar purpose -- this thread might be a way to get more material for it.)

Use as you will -- and don't forget my question. It bothers me that I have no idea what I was thinking.