Quirks are to fictional characters what favorite ice cream flavors are to regular folk: humanizing. Sure, you may hate your next door neighboor (I did that on purpose) because of all of the loud music they play at three AM when you’re trying to sleep for a morning shift at a coffee shop, but you find out that his favorite flavor is also Rocky Road and the two of you will bond like a wounded war vet and an eccentric crime-solver.
A fictional character has quirks in order to make them seem more real. Will Ferrell’s character Harold in Stranger than Fiction brushes his teeth thirty-two times in each direction. One of the Brothers Grossbart in Jesse Bullington’s book The Sad Tale of the Brothers Grossbart hates anything that has more than two legs. Xander from Buffy the Vampire Slayer always dates demon women. These things make them seem warmer to us and allow us to identify with them.
A good example of a quirk, because, just like lies, the best ones are based in the truth: a car stereo that doesn’t work when the character’s car takes a right turn, but immediately gets fixed as soon as the character turns left. (My car does this. Sir Blimey has many issues, the least of which being his propensity for trickery.) Or, because this happens to me too: the radio doesn’t work in first gear but is marvelous in all others. (In Neil Gaiman and Terry Pratchett’s Good Omens the character Crowley drives a car that turns any tape into Freddy Mercury once it’s been inserted into the tape deck for more than a fortnight.)
A bad example: anyone from The Big Bang Theory which takes stereotypes about nerds and hot chicks and then … does nothing with them. Yes, I understand it’s a show that has nerds as main characters and not just the goofy sidekicks, but comedy is only funny if it takes stereotypes and subverts them. Continually having every character wave their nerd flag is tiring and not funny at all. AND I’M A HUGE NERD.
SIDETRACKSTORY in case you don’t believe me about the nerd thing:
I walked into a comic store and was immediately ignored by the male members of staff — which were all of them — until I was ready to check out. I bought the hardcover edition of the third volume of the excellent American Vampire and was snidely asked if I even understood what they had been talking about. (They had been talking about Magic: The Gathering, which is not my cup of tea. D&D and World of Darkness — especially Mage — are my cups of delicious RPG tea.) I hatched a plot so that the next time I was there, a friend would call me and we would discuss Romulan battle techniques for a Star Trek themed RPG campaign in which we happened to be ensconced, loud enough so as to put them in their place. Now I realize the ridiculousness of it, but I wanted my nerd-cred card.
Doom comes when a quirk turns into a flaw. The Big Bang guys are hampered by their quirks and rely on them instead of using them to propel interesting plot and character development. Basically it’s like the Manchurian Candidate flaw from the World of Darkness. (Think Wolverine, who randomly forgets the things he’s done and the people he’s killed, only without the cool healing powers and the adamantium skeleton. You lose control over your character and the storyteller assumes the mantle instead.) Yeah, it sounds fun, and it may get you extra XP, but it’s no fun if someone else makes the character for you. Relying on quirks is making the audience fill in the characterization gaps. And that’s just lazy.
(There’s a meme out there of a cute kid saying THAT’S RACIST! I need one that says THAT’S LAZY! and then post it like crazy over the internet.)