The primary character is Lazy Jack. He is likely to interact with other characters in the story. For instance, he could have a mother or father figure who tries to encourage him to be more industrious. There may also be neighbors or other people in the village (if it's set in a village) that he comes across during his lazy escapades.
I'm not sure as you haven't given the details of the story, but most likely there is the lazy man himself as the main character.
I'm not sure exactly as I haven't read the specific 'the lazy river short story', but it could be a young adventurer. Someone who is drawn to the lazy river to explore and find new experiences.
Not having read the 'lazy susan short story', it's hard to determine. But if it's a story about Lazy Susan, she's the main one for sure. There might be a sidekick character who helps her in her journey or a antagonist who creates problems for her.
The main character is the lazy boy. Besides, there could be his teachers if the story is set in a school - like his teacher who tries to get him to do his work. And perhaps his friends who might either encourage his laziness or try to change him.
The 'Lazy Jack' short story is often about a character named Jack who is lazy in various ways. Usually, it shows his adventures and misadventures as he tries to get by with his lazy nature, often learning some lessons along the way.
The main character is surely Jack Frost. In some versions of the short story, there could be a human protagonist, perhaps a young girl or boy who ventures out into the snow and encounters Jack Frost. There might also be an old wise man or woman who knows the secrets about Jack Frost and tries to guide others in dealing with him.
The main characters are Jack and the giant. Jack is a young boy who is brave and a bit mischievous as he dares to steal from the giant. The giant is a huge, menacing figure who lives in the castle in the sky and tries to stop Jack from taking his treasures.
The main characters in the 'jack and jill short story' are Jack and Jill, of course. They are the two kids who go on the adventure of climbing the hill to get water.
The main characters are Jack, Jack's mother and the giant.
As I said before, not knowing the specific 'jack in the box short story', it's hard to say. But most likely, Jack is a main character since he is in the title and associated with the box.