Obviously, the main characters are the pony and the orphan girl.
As I haven't had the chance to read this 'the orphan girl short story', it's difficult to name all the main characters. But it's likely that apart from the orphan girl herself, there could be a sympathetic neighbor or a strict authority figure in an orphanage if there is one in the story. These characters would play important roles in shaping the girl's experiences.
Well, perhaps the story focuses on the bond between the pony and the orphan girl. Maybe the girl finds solace and friendship in the pony. It could also be that they go on a journey to find a place where the girl can belong, with the pony as her loyal companion all the way.
Typically, the main character is the pony girl herself. She is often a young, brave, and kind - hearted girl with a love for ponies.
In many 'the orphan girl story' variants, the orphan girl is central. Then there might be a villainous figure, perhaps someone who tries to take advantage of her situation. And there could be a mentor - someone who gives her advice and helps her navigate the difficult world she's in. For example, an old lady who has seen a lot in life and teaches the girl valuable lessons.
The main character is the orphan girl. She is the one around whom the whole story revolves. All the events, emotions, and developments in the story are likely to be connected to her experiences, her dreams, and her challenges as an orphan.
We don't really know for sure without more context. But likely, the central character is the orphan. There might also be other characters such as relatives who couldn't take the orphan in, or friends the orphan made along the way. If the story is set in a particular place, there could be local community members who were either positive or negative influences on the orphan's life.
Not having read 'the orphan boy story', it's hard to say for sure. However, the orphan boy himself is the central character. There could be other orphans in the story who become his friends or rivals. There may also be an adult figure, like a teacher or a priest, who plays an important role in the boy's life, either by guiding him or by providing some form of support or challenge.
The main character is surely the little orphan. There could be other characters like other orphans in the same place who are friends or rivals. And there might be adults in the story, like a strict orphanage director who creates some of the challenges for the main orphan character, and a friendly neighbor who offers some help or a different perspective to the orphan.
Sarah Manning is a main character. She's a con - artist who gets drawn into the clone mystery. Cosima Niehaus is another important one. She's a scientist among the clones. And Alison Hendrix, a suburban housewife clone.
Since I don't know the details of the 'ghost pony story', I can't say for sure who the main characters are. But it's likely that the ghost pony itself is one of the main characters.