Well, clearly the two crabs are the main characters.
In the two crabs short story, the main characters are, without a doubt, the two crabs. Their behavior, whether it's fighting, cooperating or just going about their own business, is what the story is all about.
Since the title mentions 'two crabs', the main characters are most likely those two crabs.
The moral could be about the importance of cooperation. In the story of the two crabs, if they don't cooperate, they might both face difficulties. For example, if they are trying to escape from a trap, but they pull in opposite directions, they won't be able to get out.
The jackal might be attracted to the crabs for food. Maybe it saw the crabs scuttling near the water and its predatory instincts kicked in. Crabs can be a good source of nutrition for a jackal.
Obviously, the two friends are the main characters. But without more context, we don't know much about their names or personalities.
The main characters in the two frogs short story are the two frogs. These two frogs are likely to have different personalities or ways of thinking. One might be more cautious while the other is more adventurous. Their interactions and how they deal with the situation they are in are what the story is all about. Maybe they are in a well or a difficult place and they try to find a way out, and all of these events are focused on these two frog characters.
The two mice are the main characters. One might be more cautious, while the other is more daring. Their interactions and individual experiences form the core of the story. For example, they could be in different habitats, and how they deal with their respective situations makes up the plot.
Obviously, the two sisters are the main characters.
I don't know as I don't have information about the 'the other two short story'. Maybe it could be a young protagonist and an old mentor type of character which is a common combination in many short stories.
As we don't know the specific 'two fisherman short story', the main characters are likely the two fishermen themselves. They are probably the focus of the story, and the events and interactions would revolve around them.
Given the title 'two kings short story', the two kings are probably the central characters. But in a short story, there could be other characters that are crucial to the development of the plot. Maybe there is a young hero who serves one of the kings and through his actions, the relationship between the two kings is affected. Or perhaps there is a wise old woman who gives advice to one of the kings, which then influences the actions of both kings. It all depends on the specific details of the story which unfortunately I'm not aware of.