Do you find it's generally the people who look mean, that are really nice?

yes. just today there was a guy like that I saw, and I squinted at him from the side of my eye while trying not to let him see that I was looking, and I thought to myself, he is scary. I will stay away from him. but it turned out he was really nice and then I could look him straight in the eye without doing the squinty thing, which is reserved for scary looking people.