The main character is Gogol, of course. However, there could be other characters who are crucial to the story. For instance, if it's a story about his first day at work, his boss or a mentor figure might be important. Or if it's in a social setting, the people who welcome him or those he has his first interactions with are also key characters. In general, the people who shape Gogol's first day experiences are the main characters in this story.
In some of Gogol's novels, there are often characters that represent different social classes. For instance, in 'Dead Souls', Chichikov is a central character. He is a rather shrewd and somewhat devious character who travels around trying to buy up dead souls. There are also various landowners he encounters, each with their own quirks and vices, and these characters together form the fabric of the story.
In 'The Nose', the main character is a nose that magically detaches from a man's face and gains a life of its own. It's a very strange and surreal character that represents the absurdity of society.
From Gogol's first day story, we might discover how he coped with the unknown. He could have met new people, faced new challenges. For example, if it was his first day at school, he might have been nervous about making friends or finding his classes. This story can give us insights into his character as he deals with these first - day situations.
Perhaps there is a young child who is about to enter kindergarten or first grade. They would be very likely to experience first day jitters. Or it could be an adult who has just moved to a new city and is starting a new job. The main characters are usually those who are in a situation of new beginnings and are feeling nervous.
Not having read 'the first day of winter story', we can only speculate. It could be a young couple who are having their first winter together and are learning to enjoy the cold days and long nights. Maybe there's a local guide in a small town who shows the newcomers around during the first day of winter, and that guide could be one of the main characters. Or it could be a family with a small child who is seeing snow for the first time on the first day of winter, and the family members are all important characters in the story.
In 'The Nose', the main character is Kovalyov, a St. Petersburg official who wakes up one day to find his nose missing. His reaction to this absurd situation and his attempts to get his nose back are central to the story.
Clifford himself is surely a main character. There may also be his teacher.
Clifford himself is surely one of the main characters. And probably his owner and his animal friends would also be main characters in the story.
The Pilgrims were a major part of the story as they were the ones starting a new life in America. And the Native Americans, like the Wampanoag tribe, were crucial. Their leader Massasoit played an important role in establishing a relationship with the Pilgrims. Squanto was also a key figure as he taught the Pilgrims so much about survival in the new land. So, these were the main characters in the first Thanksgiving Day story.
I don't know specifically without reading it again. But in Decameron stories, there are usually characters like noblemen, ladies, servants, etc. Maybe there is a young hero and a beautiful heroine in this story.