Dialects & Accents (Was Re: Subject-Verb agreement with compound subjects)

[Carol]

Potioncat: 
> <snip>
> English isn't logical. After all, a fat chance and a slim chance are
the same thing.

Carol responds:

True, English isn't logical, but the attempt to make it logical at
least makes sense. We can eliminate at least some of the obstacles for
non-native speakers, for example. Idiomatic expressions like the ones
you've cited are a bit different from rules of grammar (or the
elements of standard usage).

"Fat chance," of course, is used ironically, whereas "slim chance" is
straightforward.

How about "same difference," which is absurd, if you think about it?
I'm trying to think of another expression that I first heard when I
was about twelve years old. I recall that it grated on my nerves
because, taken literally, it meant the opposite of the intended meaning. 

Carol, hoping that the expression she has in mind will emerge from the
depths of her unconscious or that someone else will come up with it