the exception that proves the rule

This phrase has caused me more trouble than any other clichéd expression.

Many people, confusing "rule" with "law", say that anything with exceptions can't be a rule; or, if they realize that "rule" can mean "something that generally prevails or obtains" (American Heritage Dictionary), still say that the idea of an exception proving it is nonsense. So they run around contorting themselves with the claim that "proves" means "tests".

Exceptions do test rules, yes, but what are the results of the test? I see three possibilities:
1) The exceptions are so numerous or so important that the "rule" does not generally prevail at all, and ought not to be considered one.
2) The exceptions are just exceptions. The rule generally prevails but can't always be relied upon.
3) The exceptions, while still being exceptions, demonstrate why the rule is valid the rest of the time. Even though they're exceptions, they paradoxically or ironically provide collateral proof that the rule (though it has exceptions) is still a real rule, and not a phantom one (see 1 above) or a hole-ridden one (see 2 above).

Number 3 is what I think is a plain, regular-meaning case of "the exception that proves the rule." I find cases of it frequently, but I have a curious trouble remembering them afterwards. Well, I just found another one, and ( I'm going to write about it here before I forget it )

Dollhouse go boom

Did anyone else watch the final episode of Dollhouse last night, or were B. and I the last people left in the room after everyone else gave up and left?

This dismal cross between the "demons have taken over" alternate histories of the Buffyverse and John Varley's "Phantom of Kansas" period got a lot of "huh? I'm missing something, but I'm not sure what" from me, until after the show ended and I looked up Felicia Day and some of the other actors on IMDB to see if they'd been on the series before. And sure enough, I was missing something: what I was missing was the phantom unaired episode from the end of the first season, to which this one was an immediate sequel - the episode that appeared only in the DVD set of the first season, which I never got because I lacked any desire to watch this series again.

I rewatch Firefly, like, all the time. I rewatch parts of BTVS too. I've even been known to rewatch Dr. Horrible, though man, it's not holding up as well as I'd hoped. I don't rewatch Angel, though I have some of that, nor Serenity, nor this. The historical sorting process between mash and trash in Joss Whedon shows is going on very quickly as far as I'm concerned.