It all starts with an in-class birthday party for a student in Room Nine. The festivities prompt Junie B. Jones to ramble on the bus about what kind of birthday party she would want, annoying that meanie Jim, who announces that he is inviting everyone in Room Nine besides Junie B. to his birthday party on Saturday. This exclusion upsets Junie B., whose parents counsel her to ignore Jim and pretend that she doesn't want to go to the party anyway. As part of their plan, her parents get Junie B.'s grandfather to invite her over on Saturday to help fix the second floor toilet (a very enjoyable task, apparently). But Junie B. still wants to go to the party, so she tries to steal someone else's invitation as well as convince her bestest friend not to go. Her frustrations come out when she physically attempts to turn Jim's head and gets sent to the principal's office. This visit ends with the principal forcing Jim to invite Junie B. to the party. Except on the day of the party, Junie B. decides that she doesn't want to go after all (as it would mean having to take a bath and having to give a present to a boy she hates). She ends up very happily helping her grandfather fix the second floor toilet.