"Sick" is about a little girl named Peggy Ann McKay who pretends to be sick because she does not want to go to school. When she learns that it is Saturday, she decides to go outside to play.
The humor of the poem is understood by children because the theme plays upon a very common childhood stunt. Virtually every child attempts to convince his parents that he is too sick to go to school at least once and even invents symptoms as Peggy Ann does by claiming her belly button is "caving in." The poem becomes funnier as Peggy Ann's symptoms steadily build and become more dire until the climax, when Peggy Ann learns that it is Saturday. She then is suddenly well enough to play outside.
The poem was written by Shel Silverstein. It originally appeared in his collection "Where the Sidewalk Ends," which was published in 1974. Silverstein published his first children's book in 1963. In the 1970s and 1980s, he rose to fame as a beloved children's author.
Poems such as "Sick" are popular with children because they have very easy rhyme patterns. "Sick," has a rhyme scheme of AABBCCDD, meaning that every two lines rhyme. This pattern is easy for children to memorize and recall. Many of Silverstein's works feature this rhyme scheme. Silverstein's most popular works include two collections of children's poems, "Where the Sidewalk Ends" and "A Light in the Attic," and his book "The Giving Tree."