Have you ever seen or met someone — in person, on TV, in a movie, or whatever — who made you think “Oh my goodness, that’s my character!” Who was it (if you know), and what were the similarities?
I had to think about this for a long time, because while I might adopt a mannerism here or there, I’ve never come up with a character and THEN have someone remind me of them.
The closest I can come is the character of Calamus in Strange Weapons. About a third of the way into the book, I recognized that John Glover, as the Devil in the lamentably short-lived show Brimstone, made a great Calamus. After that, I kept hearing Glover do all Calamus’ dialogue in my head. In some ways, that even helped.