Most likely the main character is the grumpy old troll itself. There might also be some other characters like the people or animals that the troll interacts with, such as the villagers who try to cross the bridge that the troll guards.
The central figure in the 'grumpy old troll story' is the old and grumpy troll. In addition to that, there may be characters like a young adventurer who stumbles upon the troll's lair. There could be an old wizard who has some knowledge about the troll and its past. And there might be some local peasants who are constantly harassed by the troll's grumpy behavior.
It could be that people who cross the bridge are always noisy or disrespectful of its space. So it becomes grumpy over time as a form of self - protection.
Well, in a 'grumpy old troll story', it may revolve around the daily life of this old troll. He might be grumpy because he's all alone and has no one to talk to. The story could show how his grumpiness affects the other characters in the story, like the animals or the people who live near where the troll stays. It could also be about how the troll's attitude changes over time, for example, if someone is kind to him despite his grumpiness, he might start to become nicer.
In a 'grumpy old men story', the main characters are likely to be the old men who display their grumpiness in various situations. There might be a leading grumpy old man who is the central focus, and then there could be other old men around him who either support or oppose his grumpiness. There may also be characters like the young people in the neighborhood or family members who are affected by the grumpy old men's behavior, but ultimately, it's the old men that drive the story forward.
Since it's called 'grumpy old men quarter story', the main characters are probably those grumpy old men. But without more details, we can't know if there are any other important characters like their wives, or some local shopkeepers who interact with them regularly.
Since I haven't read it, I can only guess. Obviously, the grumpy old man is one of the main characters. There might also be people around him like his neighbors. If he has a family, family members could be main characters too, such as a son or daughter who has to deal with his grumpiness.
The main characters would be the grumpy old men. They might be retired fishermen or just neighbors who are always grumbling about life. And then there are the three bears. They could be wild bears from the forest. The old men might interact with the bears in different ways, like the first old man being really scared of them, the second one trying to shoo them away, and the third one being a bit more curious about them.
The grumpy old troll is likely to be territorial. Since it lives under the bridge, it may see the bridge area as its own. It could be ugly and big, with a rough voice. It might also be a bit smelly, as it lives in a not - so - clean place under the bridge. It probably scares people who come near the bridge by making strange noises or showing a fierce look.
The characters in the 'grumpy old men bacon story' are probably a group of old men. They might be retired and have a lot of time on their hands. One could be a former farmer who has strong opinions about bacon quality as he used to deal with pigs. Another might be a retired cook who is very particular about how bacon should be prepared. And there could be a third old man who just loves bacon but is always in a bad mood, and his friends' habits around bacon annoy him.
Obviously, the waitress and the grumpy old war veteran are the main characters. There might also be some other minor characters like the cook in the diner where the waitress works or other regular customers who interact with them in some way.
I'm not familiar with the 'the grumpy bug online story', but based on the title, the main character is surely the grumpy bug. There could be other characters like friendly bugs that try to cheer it up, or maybe some digital villains that make the grumpy bug even more grumpy. Maybe there are also some human - like avatars in the online world that the grumpy bug has to deal with.