Through a misunderstanding, Junie B. thinks that her new baby brother is really a baby monkey, and her report of this news creates excitement and trouble in her kindergarten class.
Junie B. thinks first grade is a flop when her kindergarten friend Lucille prefers the company of twins Camille and Chenille and Junie B. needs glasses.
Junie B's journal entries start with Room One's stomach virus excitement, the first-grade Columbus Day play, and getting the part of the Pinta, the fastest ship.