Jack is a young elementary school student in Miss Stretchberry's class. He initially rejects poetry, claiming his brain is empty and that he does not understand the short lines or missing rhymes of famous poems. Through a series of free-verse journal entries, he slowly begins to experiment with words and sounds. He is a sensitive and observant boy who guards his personal feelings, particularly those concerning his past experiences with his pet.

Miss Stretchberry is Jack's patient and encouraging teacher who leads a year-long poetry unit in Room 105. She introduces her students to a variety of mentor texts and creative formats, from free verse to concrete poetry. She validates her students' efforts by typing their poems on colored paper and posting them on the class board, always respecting their desire for anonymity.

Sky is Jack's yellow dog, adopted from a local animal shelter. When Jack and his father walked down the rows of cages, Sky enthusiastically begged to be chosen. He is a central focus of Jack's life and memories, though Jack struggles to articulate his deep feelings about the dog on paper.

Walter Dean Myers is a real-life, living poet whose work deeply resonates with Jack's own experiences. His accessible, emotional poetry inspires Jack to borrow his structure and eventually write his own heartfelt pieces. Myers represents the approachable power of poetry to connect with everyday life.

Jack's father is a caring presence in the boy's life. He surprises Jack with a trip to the animal shelter to adopt a dog. He affectionately greets his son with the phrase "Hey there, son!" which mirrors the language in one of the class's poetry assignments.