Teacher's Pet is the twenty-third episode of Season 7 that aired on April 8, 2010.
Tired of A.J. being a teacher's pet to Mr. Crocker and getting good grades for it, Timmy Turner wishes that he was the teacher's pet, and Poof turns him into Mr. Crocker's guinea pig. Worse, Mr. Crocker is going to use guinea pig Timmy for his experiment: a genetic hybrid of different animals creating the ultimate Fairy-catching monster!
After Timmy fails yet another quiz, Crocker tells him to be more like A.J., the teacher's pet and throws his gravity-defining pencils to his drawer (the pencil are Cosmo and Wanda). A.J. clones an apple for Crocker and creates a time machine with paper clips and yarn. Crocker lets him have holiday for the rest of the year and leaves. Timmy wishes to be the teacher's pet, and Poof (the eraser) turns him into a guinea pig. Crocker, thinking it was a gift from A.J., takes him to the Crocker Cave, where he reveals his plan, mixing the DNA of an armadillo, a dog, a Persian cat, a squirrel, and a bee to become an extreme fairy catcher. Poof tells his parents what happened, and when they are leaving to the Crocker Cave, Cosmo activated the time machine, which takes them back to when Cosmo was activating the time machine, over and over. He tries his experiment on Timmy and when it works he turns Timmy back to guinea pig form, turns himself into a bumblebee-armadillo-Persian-squirrel-dog-like hybrid, known as the Persian Bumble-Chip-Adillo Hound, and leaves.
They finally get to the Crocker Cave, and turn Timmy back to normal, he tells them Crocker's plan, and Wanda tells him the nearest fairy is Juandissimo Magnifico at Remy Buxaplenty's mansion. Crocker catches Juandissimo, stuffs him in his cheeks, and leaves. Timmy tells them to split up, and Cosmo says he will go with Wanda, Timmy and Poof. Another montage is seen where Crocker captures lots of fairies, stuffing them into his cheeks. When they realize he is heading to his lab, they try to stop him, but armadillos are immune to magic, so they think of a distraction. As Crocker was part dog, Cosmo turns into a fire hydrant. Wanda, Timmy and Poof get to the cave and create another machine out of the original one. When Crocker arrives, Timmy puts him the helmet and changes him back to normal. All the fairies and animal fight Crocker and he faints. All the fairies go to their godchildren, and Timmy wonders where to put the animals. Cosmo brings them to Timmy's house, where the Turners were watching Animal Channel, and Dad thinks its 3D/HD.