Tired of having no one to protect him from Francis and give him rides to school, Timmy Turner wishes for an older brother, thus creating Tommy Turner, an eighteen-year old brother who is perfect... a little too perfect. To turn Timmy into a model citizen like he, Tommy suggests to their parents that Timmy be shipped off to Tibecuador to perform charity work. To make matters worse, Timmy cannot wish Tommy away because Tootie has fallen in love with Timmy's nicer, hunkier brother!
The episode begins with Tootie chasing Timmy across the neighborhood. Timmy manages to evade her for a moment, and asks Cosmo and Wanda to help hide him. Cosmo poofs into a blanket and covers Timmy, Wanda sighs at the ineffectiveness of that and turns into a brick wall. As Tootie runs by, Timmy overhears her talking about inviting him to a ballet pageant. He frets as he realizes he will have to avoid Tootie's invitation before, during, and after school. Even worse, the school bus left without him. As the bus drives off, both Timmy and Sanjay are left behind.
A young man in a military uniform comes by and picks up Sanjay, revealed to be his step brother, and gives him a lift to school, leaving Timmy to peddle his way to school on a girly bike that Cosmo and Wanda poofed for him. At school, Timmy runs into Francis who was busy bullying A.J., but before Francis could harm him, A.J.'s custom built older brother robot "AJ-5000" stops Francis, who takes out his anger on Timmy.
Timmy is mad that he does not have an older brother to protect him, give him rides to school, and beat up Francis, so he wishes for one. This creates Tommy, an eighteen year old version of Timmy that is perfect in everyway, almost a little too perfect. The wish also causes Timmy's mother to age faster to compensate for the age difference. At school, Timmy explains his older brother's previous absence to his friends by saying that he was in "Tibecuador", a nation in Central America wished up on the spot by Timmy. Tommy is so impressive that A.J.'s robot self-destructs in shame that it cannot be Tommy's brother. Tootie is also infatuated with Tommy, and asks if he and Timmy want to attend her ballet pageant.
Timmy tells Tommy to let her down gently, but instead Tommy accepts her invitation and says that he and Timmy will be there.... after they are done building a hospital for the poor, that is. Tommy's perfectionist, overly moralistic behavior is beginning to wear down on Timmy. However, when Timmy tries to wish Tommy away, the wish does not work because someone is in love with Tommy. When Timmy looks outside his window, he sees Tootie standing around in Tommy-related paraphernalia. Worse, Tommy is going to have Timmy sent to Tibecuador on an eight year humanitarian mission to mold him into the perfect adult like what Tommy became. Timmy realizes the only way he can get rid of Tommy is to woo Tootie again, much to his chagrin.
Timmy goes to Tootie's house and attempts to win her back with some flowers, but she still loves Tommy and says she will donate the flowers to the hospital he built. Timmy tries again with chocolates, but Tootie scolds him, saying that Tommy told her they would give her cavities and that Timmy was not smart like him. Timmy tries again by singing a very horribly off key love song outside Tootie's window, but he only manages to win the affections of Vicky.
Timmy realizes he can win over Tootie by going to her pageant, while stalling Tommy. He has Cosmo pose as various distractions, like an orphanage of tone deaf orphans, or an old man having a heart attack, so that Tommy cannot get to Tootie's ballet pageant on time. At the pageant, Tootie is crying when she sees that Timmy and Tommy's reserved seats at empty, but she falls back in love with Timmy when he shows up. With Tootie's love no longer in the way, Timmy is able to wish Tommy away and resume his normal life. This causes his mother to age back to normal as well.
Timmy is satisfied with being an only child, although he and Wanda cannot help but wonder what became of Tommy. In Tibecuador, a tribal version of Timmy is boasting about his new older brother that will help him beat up "Francisco", but Tommy instead wants to help save an orphanage of tone deaf llamas in need of heart surgery. The episode ends with tribal Timmy saying "Oh Brother".