You know what they are: Art Quirk, American Major League Baseball player. Billy Quirk, American silent film actor. Daniel Quick, American professional wrestler---WAIT, WAIT, WAIT. That's not the kind of Quirks I'm talking about, although I have no doubt they lead interesting lives.
I'm talking about quirks: odd mannerisms, peculiarities, something that makes you, YOU. Quirks let you know who you're dealing with, throwing out clues as to their character and demeanor. Or it may cause you to wonder about them even more. You either Love 'em or hate 'em. The quirks, not the people. Unless the quirk is really annoying and then yeah, Hasta la vista, friend.
For writers, quirks are what make people interesting. It's what separates one character from one another. They give you clues as to the perpetrators. Give bullies a purpose in life. They're...quirks.
What are some of your favorite character quirks? Who writes quirkiness really well?