Timmy asks A.J. if he could borrow A.J.'s new invention, The Youth-Inator 1000 (A.J., Of course, Says yes). But after Timmy accidently zaps Cosmo, Wanda, Anti-Cosmo, and Anti-Wanda with the Inator, they all start aging backwards until they revert back to their infancy. And to make things worse, Crocker steals the Inator! Can Timmy get them back to normal?
The episode starts with Show-And-Tell Day at School. Francis (for the hundredth time) shows his dog, Mange. Then, After Francis finishes his stories, A.J. comes up to show off his new invention, a Rejuvenation Ray. He claimed its main goal was to transform anything into a younger version of itself; He called it "The Youth-Inator 1000". Then, To demostrate for proof, A.J. blasts one of the students and turns her into a baby. Timmy was amazed by the Inator's effects. Crocker stares stunned and startled by the Inator's effects and says to himself: "If I can steal that Youth-Inator, I can use it on any Fairy I see and use their more-powerful-than-adult-fairies powers to conquer Earth and gather all of its inhabitants and riches, So people will finally believe that FAIRY GODPARENTS exist!" But A.J. warns everyone about the catch of the Ray. Even if you are zapped, You will still age backwards, Meaning you shall grow younger and younger until you seize to exist. Everyone in the room gasps, And A.J. walks back to his seat, Bowing.
At lunch, Timmy cannot stop staring at A.J.'s machine, And he tells Cosmo and Wanda (Deguised as Timmy's food once again) that he could not take anymore, And that he wished he had the Inator. Wanda then tells Timmy that that would be stealing, And Fairies cannot steal things from other People; But if he asked A.J. nicely, He could probably borrow it. Timmy agrees with Wanda, and scoots closer to A.J. Timmy then asks if he could borrow the Inator for the day, And A.J. agrees, As long as he gets Trixie for the week. Timmy says yes, And A.J. hands over the Inator, Just as the School Bell rings.
Timmy, Cosmo, and Wanda walk (and float) in past Anti-Cosmo in a prison cell, and Anti-Wanda playing with Poof (She had promised not to hurt him). Wanda asks Timmy if he had fed Anti-Cosmo yet, And Anti-Cosmo replies that he didn't, And he was so hungry he had to knaw his own arm off. Cosmo, Wanda, Timmy, and Poof scream, And Anti-Cosmo says he was kidding, And that he had broken out and gotton some food out of the kitchen. Timmy asks everyone if they would like to become his Test Subjects. Everyone agrees. But, Cosmo grabs the Inator and says he can make this old piece of pizza young again. Then Cosmo throw the pizza into the air, And aims the Inator at it. He misses, And the bolt bounces off the ceiling, And zaps Cosmo, Then Anti-Cosmo, Then Wanda, Then Anti-Wanda. Timmy and Poof take cover under a table. Timmy looks up to see four fairy teenagers: Wanda as a Cheerleader, Anti-Wanda as a Cheerleader, Cosmo as a Skateboarder, and Anti-Cosmo as a snooty teen reading a book and sipping tea. Timmy grabs the Inator out of Cosmo's hands, And scolds him.