In 'The Neverending Story', the little old man could be Cairon. He is a wise and somewhat mysterious figure in the story who often guides the main characters and plays an important role in the fantastical world of Fantasia.
It could be a new character created by the fanfic author. Maybe a young vampire or a human with some special abilities that are related to the Twilight lore.
It could be one of the many minor characters in Pulp Fiction, like the guy at the diner who witnesses the crazy events but has no real name. Maybe it's a way to give him a bit of a story for his birthday.
Maybe the 'little old me' represents an introvert. Introverts are often quiet and keep to themselves, which can make others around them feel a bit uneasy or even fearful in some cases. The story could be about how this introverted 'little old me' gradually shows their true self, which is much more complex and interesting than others initially thought, and how the others come to accept and even respect them.
Since we don't have much information about this specific 'blackkklansman old man story', it's difficult to say who the old man is. He could be a fictional character created to represent the older generation's experience with the KKK - related events in a story based on 'BlacKkKlansman'.
In 'the old man at the bridge story', the old man is an ordinary person whose life has been upended by war. He seems to be a bit forlorn and lost. He has his own little world back home with his animals, but now that world has been destroyed by the war. He is at the bridge, a sort of liminal space between the past and an uncertain future. He represents the countless individuals who are displaced and left in a state of confusion and despair during times of war.