Jill And The JogeroBook - 1992
At the age of four or five most children being to print letters, then their names. After this, they go on to compose words which they confidently expect will make sense--to someone.
This is the basis for Richard Thompson's story. Jill's father believes that JOGERO (as Jill prints it) is just gibberish. But there really is a JOGERO that Jill has seen. Her father is skeptical--but the JOGERO, an imp in the sandbox, creates mayhem in the backyard until he's taken away--under control, by his master.