Harold and the Purple Crayon is a 1955 children's book by Crockett Johnson. This is Johnson's most popular book. It led to a series of other books, and inspired many adaptations.
The protagonist, Harold, is a curious four-year-old boy who, with his purple crayon, has the power to create a world of his own simply by drawing it.
Harold wants to go for a walk in the moonlight, but there is no moon, so he draws one. He has nowhere to walk, so he draws a path. He has many adventures looking for his room, and in the end he draws his own house and bed and goes to sleep.