Without more information about the episode, it's hard to say exactly what the story is. It could range from a fictional tale Roz made up on the spot to a real - life adventure she had. It might also be a story with a moral, like how being honest always pays off or something similar.
One possible theme could be mystery. The use of 'black' in the title often implies something unknown or hidden, so the story might revolve around uncovering secrets.
I'm not sure specifically as there are many episodes of Frasier. It could be a humorous anecdote, a personal experience, or something related to their work at the radio station. Without more context about the particular episode, it's hard to say exactly.
He might be surprised. If Roz tells a story full of unexpected twists, Martin could show his astonishment through his facial expressions or some short exclamations.
I'm sorry, but without more context regarding 'matin hati's black story', it's impossible to provide a comprehensive response. It could be a story about a particular place called Matin Hati that has a history associated with the color black, perhaps something to do with the local environment, traditions, or historical events that are somehow connected to the concept of black.
Martin Pistorius in the story is a man who endured a long period of being locked within his own body due to an illness. He was someone who defied the odds as he slowly emerged from his non - communicating state.
I'm not aware of any extremely popular ones specifically about Martin getting hurt. However, popularity can be subjective. What might be popular among one group of fans may not be known to others. As I mentioned before, checking the major fanfiction platforms is your best bet.