Names tend to stick and sometimes you name your characters for silly reasons. But, what when you hit a certain point in worldbuilding where you realize you want to change most of the characters' names (including the main protagonist) to follow a newfound theme in the story? At first glance doesn't seem much of an issue, but when you think of a certain person as "Mary" for long, it's hard to change, you decide to rename her "Kate" but your brain still thinks of her as "Mary". Is it desirable to change identification of a character late into story development? I referenced names in the thread title but also applies to appearance I believe. Personality is unique and very difficult to change, so let's not get into that.