I love it when characters surprise you, just like real people. When I write a scene I just try to make the characters behave in a way that feels natural to them. Sometimes that means they make a left turn and do something unexpected. Those are always the best scenes in my opinion.
For years, I've had a hankering for the portrait of Benjamin Franklin by Joseph Duplessis. Franklin is credited with so many inventions: the postal system, lightning rods, the constitution. He was a rock star before there was such a thing.