If characters are overstuffed with mannerisms, they’re gaining in quirks while losing in depth. Quirks and idiosyncrasies, moreover, should have a function.
Recently, I watched the indeed infernal movie adaptation Ghost Rider by Mark Steven Johnson from Marvel’s graphic novel series of the same name, starring a CGI motorbike and Nicolas Cage as Johnny Blaze. I’m still stunned by how bad it was. And, honest to goodness, I can take a severe beating from a movie as long as Nicolas Cage is among the cast.
Now one of the things you wouldn’t want to do to a character in your novel, short story, or screenplay, is what they did to Johnny Blaze: stuff’em to death with quirks and idiosyncrasies. Make ’em Mr. and Ms. Mannerism. Watch the movie and see what I mean. Or, come to think of it, don’t. Imagine a character in funny costumes with a single-minded, peculiar occupation, who keeps his motorbikes in his living room, is a teetotaler, and slurps brightly colored candies from a cocktail glass while watching comedy shows with chimpanzees in it, exclusively. For starters. Oh, and not to forget an eternal bad hair day.
I’ve come across such overkill in mannerisms rather often (though not in major feature films; that’s a new one). First takes on science fiction, fantasy, or cyberpunk from inexperienced writers. Role-playing characters, especially, players and non-players alike. Of course, everyone’s advice is “be specific,” and indeed, generic descriptions as “handsome” or “smart” and the like are not an improvement. But what your characters gain in quirks, they quickly lose in depth.
And that’s not all. Quirks and idiosyncrasies should have a function. Each. At one end of the spectrum, they’re a handy device to differentiate one character from another. But if you pull out all the stops, nothing is gained with such a quirk inflation with respect to differentiation. At the other end of the spectrum, quirks can hint at important characteristics, i.e., important for the development of the story. (Like, say, in such a way that it lets a character make certain kinds of decisions.) But these have to be meticulously developed and extensively fine-tuned in order to work at the right moment. The more quirks your characters have, the more arbitrary they tend to become, or come across as such because you don’t have the time and space to make them relevant.
And if they’re not relevant, if they can’t scaffold developments and decisions, then their existence in your story is simply not justified.