When Timmy brings an actual dinosaur to class, his class doesn't believe him, but his demented teacher Mr. Crocker soon figures out that Timmy actually used fairy godparents to create such a creature. Having insisted his whole life that fairies exist, Crocker plans to capture them when he forces a meeting with Timmy's parents who need to be replaced by Cosmo and Wanda to hide the truth. Meanwhile, Chester and A.J. are asked by Timmy to capture the dinosaur to recover the evidence. But the situation turns out to be harder than they thought, with Crocker struggling to discover the truth at almost any cost.
It is show and tell at Mr. Crocker's class. Francis is showing off his dog Mange, who he feeds first graders to keep his dog's coat shiny. Mr. Crocker gave him a "D", the first letter in dog. Timmy was up next, and with Cosmo and Wanda's help, he was able to wish up a tiny extinct dinosaur called a Pollywollyoptasaurus. Mr. Crocker was about to give Timmy a "D", as in the first letter of dinosaur, when he suddenly realized that the only "logical explanation" for Timmy genetically engineering a real alive breathing dinosaur was "Fairy Godparents!", which Crocker spasms into unearthly motions as he screams out, something that will remain a running joke and stable of his character for the rest of the series. He then told Timmy he was going to request a meeting with his "real parents". Meanwhile, the small dinosaur escaped, and after school Timmy calls Chester and A.J. and asks them for help in finding it.
Timmy is somewhat upset that Cosmo and Wanda ruined his show and tell (which they apologize for), but even more so that he needs to explain how he got a dinosaur to his parents and Mr. Crocker. Cosmo and Wanda offer to help by posing as Timmy's parents. Timmy trains them rigorously in acting human, as they struggle with things like walking through doors, and even basic involuntary human needs like breathing. Meanwhile, Crocker is already going nuts at the thought of his theory of Fairy Godparents actually being right. He hopes to steal their magical power so he can rule the world, and have revenge on Principal Waxelplax and another teacher that crack jokes about him by the water cooler. He goes to his "Crocker Cave", a phone booth in the janitors closet, where he uses a Magic Detector to sense for Timmy's fairies. He also sets up a trap in the parking lot, a crude sign that reserved a parking space for "Fairies". It nearly works, and Crocker will have "all the proof the world needed", but Timmy narrowly averts disaster by swerving the car into the teacher's space.
Meanwhile, Chester and A.J. are searching for the Polywolyoctasaurus when Mr. Crocker catches them. He offers them a deal, to capture Timmy's dinosaur and bring it to him so he could show it to Timmy's parents, in exchange for a seat of power in Crocker's "new world order", which they eagerly accept. Timmy walks in, with human Cosmo and Wanda walking in eagerly behind him. Timmy tells them to play it cool. When Mr. Crocker goes to shake Wanda's hand, she throws him against a wall, thinking it was a better handshake. Crocker devices a plan, he hooks a chair placed in a large bucket of water up to electricity, stating that if they survive they are "FAIRIES!", if they don't then at least he has "TENURE!". Cosmo randomly offers Mr. Crocker a fish, causing him to drop it, slip on it, and then land in the electric chair, badly shocking him and turning the fish he was holding into fish sticks. Crocker leaves to "chip off all the dead skin", Timmy tells his godparents to "be on their toes", they go on their toes literally and fall over. Timmy remarks, "I'm doomed."
Chester and A.J. have tracked down Timmy's dinosaur, they almost manage to corner it, but it runs into the "forbidden zone", the girl's bathroom. Chester and A.J. argue over who is going in but they end up entering it, while back at the parent-teacher conference Crocker offers Cosmo and Wanda coffee, with a helping of milk, cream, sugar, or magic. Chester and A.J. finally go in together and capture the dinosaur. Cosmo and Wanda are overexcited from the coffee and about to give themselves up, when Wanda needs to use the bathroom, some she has apparently never done before. Crocker tries to trick her with a choice, "Boys, girls, or mystical creatures". She is about to choose the third option, when Principal Waxelplax strolls by and goes in first. Waxelplax ends up getting tied up by toilet paper in a trap Mr. Crocker had placed in the bathroom. She screams "CROCKER!!!!" in anger while the others follow her into the bathroom.
At the same time, Chester and A.J. arrive, having captured the dinosaur and placed it in a box. Crocker reminds Chester that he'll give him a position of power in the "new world order" he is going to create when he reveals fairies exist, but Chester gives it to Timmy instead, declaring "Before school hours, you ain't the boss of me." Crocker snatches it anyways, but not before Cosmo and Wanda change the dinosaur in the box into Francis' dog Mange, who bites Crocker's leg. Principal Waxelplax gives all four of them detention, Timmy for faking his show and tell, Chester and A.J. for going into the girl's bathroom, and Mr. Crocker for trapping her in a cocoon made of toilet paper and promising two small boys they could enslave the Earth. Waxelplax claims that is not right before leaving. Timmy is relieved he has averted disaster, but Crocker is onto Timmy and his fairies, and he'll have to be extra careful around him from now on. Crocker vows that "They can't keep him in detention forever", until Principal Waxelplax backs up into the "Fairies" parking space trap he made earlier, causing her car to fall into a pit. She screams "CROCKER!!!" one last time while Timmy remarks on Crocker about possibly of keeping him in detention forever, "Maybe they can". As the episode fades to black, Cosmo leaps across the screen, still hyperactive from the coffee.