The central character in 'the sad caterpillar story' is the caterpillar. But there may be other characters in the periphery. There could be a group of ants that the caterpillar encounters. The ants could be busy gathering food while the caterpillar is just sad and lost. There might also be a caterpillar family that the sad caterpillar belongs to, and they either don't understand its sadness or are trying to help it in their own way. And then there could be the plants which are not exactly characters in the traditional sense but are important elements as they are the source of food and shelter for the caterpillar.
As I don't know the exact sad peacock story, it could have the peacock as the main character, of course. There might also be other animals like a sly fox that teases the peacock or a kind deer that tries to comfort it.
There's no way to know for sure without more information. It could be a young child who has to endure a difficult life situation in the sad story. Or it could be an old man looking back on a life full of regrets. Maybe it involves a group of people, like a family or a community that has to deal with a sad event together.
The piggy is the central character for sure. If it's a story set in a barnyard, there could be other characters such as the hens that might be indifferent to the piggy's sadness, or a dog that guards the farm and might either be a threat or a potential friend to the piggy. There could also be a wise old owl in the nearby tree that the piggy might look up to for advice or comfort in its sad state.
In the 'the sad peacock story', the main character is of course the sad peacock. There could be other characters like the peacock's keeper if it's a story about a captive peacock. Or there could be other birds or animals in the forest where the peacock lives. For instance, there might be a wise old owl that tries to console the sad peacock or a mischievous monkey that teases it, adding to its sadness.
I'm not really sure about their exact ages. But often in such stories, the ages of the characters play a crucial role in shaping the plot and the emotions involved. Maybe the boy is a bit older or younger than the 15-year-old girl.
Another possible main character could be a wise old mermaid. She might have tried to warn the sad mermaid about the consequences of her actions, like falling in love with a human or making a deal with a sea witch. Her warnings, though well - intentioned, might have been ignored by the sad mermaid, leading to her current sad situation.
The sad prince is the central figure in the story. There could be other characters such as the poor citizens in his kingdom. They are important as they are the ones whose suffering the prince witnesses. Maybe there is also a messenger or a court jester who adds some color to the story and helps to show different aspects of the prince's character through their interactions.
I'm not sure as the title doesn't give specific details about the characters. But usually in a sad love story, there would be a couple, like a man and a woman in love. Maybe there's a protagonist who is deeply affected by the sad events in the relationship.
One possible main character could be a Pikachu that lost its trainer in a storm. The Pikachu then has to search for the trainer all alone, facing all kinds of dangers in the process.