So, having spent the large majority of the night laughing our asses off at the worst fanfic that has ever happened to anything, anywhere (see Bean's post below), we watched some canned TV. I won't divulge the series, in case of spoilers, and while it seems that rambling about TV at twenty after one in the a.m* seems...random...it does have a point. About characters. And killing them off.
Now, I get that it's not always possible to keep actors from season to season, due to contracts, and other jobs, and life stuff, and...maybe they're horrible bastards/bitches to work with and no one likes them in real life. Or maybe not. Sometimes the writers are just assholes. Whatever. There are times when a writer has to make a decision about what to do with a character, and it usually boils down to a few options:
a) Send them on a 'vacation' that lasts a very long, long time
b) Kill them off
c) ...I had a 'c', but I can't remember it right now.
How a writer (for anything, TV show, book, short story, etc) handles that character's departure is a delicate, delicate thing. Especially if you've got vocal fans, and especially if you're going with option b).
I don't want to say that there are rules, but there are...sort of. Well, guidelines. Like 'Be Consistent'. If a well-loved character is about to get offed, at least make it make some sort of sense. Don't do it because you think ratings will go up, or to sensationalize it, because that just cheapens the experience. And it cheapens the characters.
If your characters are really that good, your audience will (on some level) believe that they're real. It's how our minds work. We personify everything. This doesn't mean they'll write horrific fanfic about it, or even good fanfic, but they'll keep watching the show/reading the book. They'll keep searching for that connection they felt.
Removing that connection will leave a hole, even just a tiny one. We all want our own deaths to mean something - it's another consequence of being human. A beloved character dying, seemingly at the whim of an author and for no other purpose...there is no meaning there. It leaves the audience confused, hurt, angry, and a little afraid. Then they stop reading/watching, which is the exact opposite of what you, as an author, want.
This leads naturally into 'Remember Your Canon'**. If you're going to turn a character into (for example) the murderous sidekick of an recurring cannibalistic villain because you don't want to bother developing him any more***, at least make sure there isn't an episode earlier in the series that won't make it extremely obvious what you're doing.
Art, in any form, is about evoking emotional responses from your audience. There's also a very close tie to our biological need to reproduce, but that can be a topic for a different post. Even if you're in it only to make money off the masses, you should still remember that 'art=emotion'. Killing a character will trigger that emotional response very quickly, and if that's what you're going for, then yeah...it works. It can just as easily backfire, though. So be careful.
Oh! I remembered option c) have them switch sides long enough for people to begin to hate them, and then kill them off****. This, too, has to be done delicately. If there's no basis for having them become turncoats, then your audience won't believe it. And if they can't believe it, they won't keep watching/reading. Their emotional ties will be severed.
Whatever. Sometimes, killing your own characters is unavoidable. Sometimes, you've killed them off before you've even realized what you were doing, sometimes it's a premeditated removal of a character. Whichever it ends up being, and whatever comes after, do it well. You owe your characters that much.
* It was 1:20 am when I started writing this, but...I was much too tired to finish it, so now it's the next day.
** Not the explosive device. The other one. I can never remember which one has two 'n's.
*** I'm looking at you, Bones.
**** Goddamnit, Joss Whedon