|Or is it?|
Sometimes you really did overlook something, and your concept isn't something you can pull off in your current game system. For example, alignment restrictions stop you from fully realizing a barbarian/paladin in Pathfinder, because you're going to lose access to one of the class's abilities. While you could play a thin-blooded vampire who walked in the daylight in Vampire: The Masquerade, the same option isn't available in Vampire: The Requiem (though there are alternative methods in place). The fifth edition of Dungeons and Dragons doesn't have firearms, so you can't bring a gunslinger to the table.
Those are all mechanical reasons a character concept won't work in a given game. When a player imposes his or her own personal beliefs about what classes/characters should and shouldn't be with no backing from the rules, though, that's called concept policing. And really, it's something we should all learn not to do.
If The Rules Don't Prevent It, Why Should Your Opinion?
This bears repeating. If the only objection you have is, "that isn't how I picture that class/race/archetype looking or acting," then that is not a legitimate reason to tell someone else they can't play a certain concept. Disagreement is fine, and we should all feel free to discuss the merits of concepts openly and respectfully, but if the only reason you feel a concept won't work is that you disagree with it, then that is the weakest excuse you could give for why it shouldn't show up in a game.
|There is no room for weak sauce at the gaming table.|
As I mentioned in What's In A Name? How Your Character's Class is Limiting Your Creativity, it's very easy for us as players, and even as DMs, to get wrapped up in what we think a certain character has to be. For example, rogues don't have to be dexterous sneak thieves who pick pockets. They can be, but they aren't required to be. The same goes for the knights in shining armor we typically think of when paladins come to mind. We could just as easily have a chivalrous, god-fearing fighter with a strict code of ethics inside that suit of plate. Alternatively, the foul-tempered, disreputable-looking woman in boiled leather and chain with the longbow might actually be the one with paladin levels, doing noble deeds with no need to boast or brag.
There's also the important point that your class is a meta concept. We know, as players, what someone's class levels are. But those class levels, indeed the very concept of a class and levels, is something that doesn't exist in the world we're looking at. So, while the king's bodyguard might be a hulking northerner with a war ax on his belt, his sheet might declare he has 9 levels of samurai. And while the party's face man may seem unremarkable, barring his silver tongue and winning smile, he might boast levels of ninja. Not because he wears black pajamas and throws shuriken, but because he's a spy who's received government training in the arts of infiltration, combat, and when necessary, assassination.
The Flip Side
On the other hand, it is important for players to remember that their concepts need to follow the rules. That includes the established rules of the game system, as well as the declared rules of any pre-generated adventures, the established canon of a setting, or the house rules in play at a given table. If the DM has clearly stated things like, "no evil PCs," or, "no races other than the base races in the core book," then you can't claim your concept is being policed when you want to play a lawful evil Drow necromancer.
|Or, really, any kind of lawful evil necromancer.|
Also, there's a big different between having your concept policed, and having it criticized. Ideally, criticism will examine aspects of your concept, and question why it has to be a certain way. Things like, "who taught your character this obscure martial art?" or "if your character's family was killed in an orc raid when she was five, then who raised her to adulthood?" Criticism can point out flaws and underdeveloped sections in your story, or offer alternative ways to make the concept even stronger. Policing is someone saying, "I don't agree with/like this, therefore it is wrong, and you can't do it."
Keep An Open Mind (And Open Ears)
With everything that's been said, the key is for all of us to listen to each other. We're all working together to try and have fun, tell a story, and create something with our own, unique spin. With all the creativity we have as gamers, why limit our character concepts beyond what's already being imposed by our systems and setting of choice?
Also, while we're on the subject of characters that defy the norm, you should check out my Unusual Character Concepts page, if you're looking for new ideas to bring to your table.