Last week I found a new character.
I had been writing a scene in which the protagonist was about to do something to advance the plot and I was reasonably happy with how I viewed him and what he was doing. As I did so, I put some words into his mouth that, about two seconds before I did so, I didn't know I was going to and ta-dah! – I had him nailed. For me, everything I know about this individual is summed up in that short piece of dialogue. I can see him, can easily envisage what his life has been, and can dictate what he will do down to when he'll scratch his nose. (If it advances the plot, that is.)
And that line is?