"THAT was the wrong thing to say..."
We all know the KIND of scene: one character talking to another, and the one character makes some bold statement which the reader just KNOWS is the absolute Wrong Thing To Say To That Character. Some of them are too obvious to be, in and of themselves, memorable -- for instance, characters with kneejerk reactions to some particular offense (in anime, Lina Inverse's reaction to comments about her chest size, for instance). The ones that stay with us are ones that are pretty much unique, not just common running gags.
My current favorite comes from the first season "Clone Wars" DVD. Assaj Ventress has just defeated all contestants in an arena and makes a claim to be Sith to Count Dooku. Dooku finds this amusing and points out that, basically, while she LOOKS like a Sith she isn't a Sith, because the Sith knew no fear, "And I sense much fear in you." (echoing Yoda's comments to Anakin, interestingly enough).
To which Assaj retorts, sneeringly, "You are a foolish old man who knows NOTHING of the Dark Side!"
One can tell that this both amuses Dooku, annoys him, and perhaps startles him by its sheer WRONGNESS. Which he of course proceeds to demonstrate rather conclusively to poor Assaj Ventress.
So, what examples of this do y'all have that come to mind?