There are exceptions.
Even if most of the troubles you'll encounter are the result of characters that don't quite work for whatever reason (something we're all guilty of), there are certain players who are going to cause problems no matter what. And I'm not talking about the guy who always makes the same character with minor setting adjustments. I'm talking about the players who will make you actively dislike the game you're playing, the cases where you're going to need to address the problem beyond just shaking your head at one character or another. These guys exist, and even though they're not the majority, they have an unpleasant impact.
Pen-and-paper games have a major advantage over MMOs: They've got dice. Anyone can fail an important roll at a crucial second, and it's hard to feel like the greatest thing since sliced bread when you just accidentally swung your sword into the princess you were trying to rescue rather than her kidnapper. There's a complex system of balances in place to prevent your character from being the best at everything, and short of cheating on rolls, you're going to have to accept some weakness.
Not so with the Champion. In fact, you probably encountered the Champion when you were young; he's the kid who always insisted that whatever happened in a game didn't really happen to him. When you were running around pretending to be superheroes and the kid playing Doctor Doom said he shot a beam that killed everyone, the Champion was the kid who immediately shouted "nuh-UH!"
Actually, wait, that was every kid. Those games were really stupid.
Of course, they were stupid mostly because nothing bad ever happened to anyone thanks to the invisible protection of the "nuh-UH" field that nullified any concept of actual danger. You've hopefully grown out of that phase by now. The Champion hasn't. So even though you now understand that part of the fun of roleplaying is being injured or beaten and still trying to triumph over adversity, the Champion is still shouting "nuh-UH!" And just like before, that pretty much obviates any sense of danger because you know that his character is never going to do anything other than succeed and be invincible.
What you can do: There are two kinds of people who fall under this header. The first is made up of younger players and players not terribly aware of how storytelling works, and these people you can usually set right with some earnest explanation. Demonstrate how much more important it is to have a fallible character, encourage the player to work from weakness instead of strength, and above all else, give him or her time to mature. There's nothing wrong with youthful enthusiasm.
The other kind, however, is trying to fix everything in roleplaying because his or her real life is a disappointing mess. You can try and convince the player in question to take a different approach, but it might be better just to avoid roleplaying scenarios where success or failure is a possibility. ("Go fix your life" isn't bad advice, but it's pretty useless.) Stick with character interactions and lower-key events.
If you don't get the reference... really, how I envy you.
All characters are informed to some degree by the person playing them. I've talked before about degree of investment in characters, but even if you're making a character who's intended to be your polar opposite, you come into the game with your own preconceptions. That character reflects you in some small ways, even if just in the sources of inspiration you've chosen. That's perfectly fine.
The Mittens, however, takes this to a disturbing level. The Mittens isn't always playing an idealized version of himself, but he is always playing a character who can say what he wants to and excuse it as being character speak.
Let's say that Mike has made a character, and he explains to everyone that the character is meant to be racist against elves. It's an interesting concept, sure. Of course, then you notice that Mike's character also is saying some racist things about non-elves. Also a lot of misogynistic crap. And then there are his Dave Sim-style rants about politics... and eventually you get the feeling that this isn't what Mike's character is thinking. It's what Mike would like to say normally, and he has an excuse here.
It can be almost anything. Maybe it's a character who wants to sleep with everyone, maybe it's a political pundit who's veering directly into real-world issues with gusto, maybe it's a character who just loves to say nasty things that sound a lot like personal attacks. Whatever the case, this player isn't making a character to roleplay; he's making a sock puppet. And odds are good that said puppet is not espousing views you find terribly pleasant in the first place.
What you can do: Keep discussion on a character level. Mention to the Mittens in OOC chatter that his character is really over the line for the relevant reasons. If he persists, it might be time to pack up and move shop, since you're probably not going to change someone's personal beliefs or habits over a roleplaying debate. There's room to ask questions about why the player enjoys playing reprehensible characters, but that's rarely a line of questioning that works out well.
OOC communication is a great way to avoid drama... usually. Every so often, you run across someone whose character isn't the problem when it comes to drama -- the player is. The character may be completely inoffensive, but somehow the player manages to turn even the calmest discussion into an enormous shouting match.
The "why" varies a lot. Sometimes the player just has a penchant for offensive jokes and sticking her foot in her mouth. Other players are intensely high-strung and take even offhand remarks as personal slights. Sometimes it's not even an obvious conflict, just a bizarre case of a player who gets into arguments despite trying to avoid them. Whatever the case, the net result is the same: The real problem is the player's demeanor rather than character's.
Normally, this is something that's not going to come up right away because the player's characters aren't the sort who necessitate a lot of OOC interaction. It's the sort of thing that's only going to come up after a long period of roleplaying, at which point it's going to become a very severe and obvious issue. If the Mittens is an offensive character based on what seems to be an offensive person, the Bickerer is an offensive person (intentionally or otherwise) lurking behind a perfectly normal facade.
And since the usual way to avoid drama is to talk about things OOC, this is a huge issue. It means you either plunge ahead relentless IC and risk causing drama (thereby giving the Bickerer ammunition for a huge storm of dramatic argument), or you bite the bullet and... launch directly into a huge storm of dramatic argument right away. So there are no great solutions.
What you can do: Understand that this person is a time bomb. Sooner or later, OOC is going to drift into IC, and that penchant for drama is going to make a mess. If the person in question is a good roleplayer and you don't want to just move on, your best bet is to just batten down the hatches ahead of time and wait for the storm to hit because it will hit, and you can at least sit it out in relative calm.
Not my problem
Problem players generally are best handled with kid gloves. Problematic characters can be fixed, but players who bring problems by their very nature generally can't. Sometimes the problem might really be that you just like a different style of game. With players who just rub you wrong, make an effort to minimize their impact on your experience and move on.
As always, feedback is welcome in the comments below or via mail to firstname.lastname@example.org. Next week, I'm going to answer a very simple question with a complicated answer: Why bother with roleplaying?
Every Friday, Eliot Lefebvre fills a column up with excellent advice on investing money, writing award-winning novels, and being elected to public office. Then he removes all of that, and you're left with Storyboard, which focuses on roleplaying in MMOs. It won't help you get elected, but it will help you pretend you did.