Timmy wishes he was the smartest kid in the world, but the situation becomes complicated when he is placed in a competition with A.J. and loses his intellect when he realizes that Da Rules forbid magic assistance in winning a competition, as it is cheating. He requires the assistance of A.J. to help both of them win the contest.
Mr. Crocker is handing out the test results to his class. A.J. of course, has an "A" which is sparkling with gold stars. Timmy did not study, because Cosmo convinced him to play the "not study game" (a.k.a. throw aside his books and play video games). Mr. Crocker hands Timmy an F, soaked in so much red ink it looks bloody. A.J. brags about his test score at the lockers to Timmy, A.J.'s locker is full of A's and Timmy's is packed with F's. Timmy tells A.J. to knock it off because he is not in the mood, but A.J. tells him he is jealous and that he should study harder. A.J. offers to help Timmy bring his "F to a D" but Timmy scoffs at him. A.J. smirks and tells Timmy to spell "calculator", Timmy fails to do so and walks off annoyed. At home, his parents ask Timmy what this F means to them. Timmy says that it's his fault and he can do better, and his parents scream in relief because they thought it was their fault and that they would have to blame themselves, so they send Timmy to his room and tell him to apply himself.
In his room, Timmy tries to read a book, but he does not even make it past the title of Chapter One before he is overcome by boredom and concludes he is done. Timmy is back to playing the Crash Nebula video game, when his phone starts ringing. On the other end of the line is A.J., who hears the video game in the background and tells Timmy that he should be studying. Timmy asks "What are you, my mom!?" and slams the phone down, but puts it down the wrong way and misses the receiver, A.J. mocks him a few more times before Timmy is able to place the phone down right. Timmy fumes about A.J.'s superior intellect to his godparents, and then realizes he can just wish to be smarter than A.J. He wishes that he knew everything. Cosmo and Wanda raise the wands and grant the wish, Timmy's cranium swings up and all the books of the room cram into his head. Wanda poofs them to a gameshow and asks Timmy and Cosmo what the most abundant substance in the universe was. Cosmo said "pudding", while Timmy correctly guessed "hydrogen" and also answered the rest of the questions before Wanda even gave them.
At class the next day, Mr. Crocker is about to give A.J. his usual A, but Timmy steps forward and finishes the sentence Crocker was about to say. He then quickly teaches the class about the Alamo and the state of Texas. Mr. Crocker asks for A.J.'s A and gives it to Timmy as the class cheers, and A.J. shoots a glare at Timmy. At the lockers, A.J. asks Timmy what his scene in class was all about. Timmy says that he is just beating A.J. at his own game and mocks him the same way A.J. did to him earlier. A.J. says that Timmy being smart for a day is no big deal, but Principal Waxelplax walks by and disagrees. She offers Timmy a place on the "Academic Brain-a-thon", first chair. A.J. protests that he always gets first chair, but the Principal assures him he will get get second chair, A.J. asks what the difference and Timmy says "One chair. DUH!", he and the Principal laugh as A.J. walks off angrily.
At home, Cosmo and Wanda gasp in horror as Timmy begins to mock his parents intelligence. His father misspelled "college" on his Harvard application. His mother tells him its time to go to bed because even though he is a genius, he is still ten years old. Timmy says that if her math skills are anything like Dad's spelling, he could very well be 21 by now. This angers Mrs. Turner who says that Timmy can make fun of her math skills until its "thirteen o clock" but he cannot act like a smarty pants. Timmy asks them to prove he was a smarty pants, and then gives a long scientific monologue about the perception of objects in the universe, leaving his parents stunned and his father with a headache. Back at school the next day, the Brain-a-thon is taking place in the auditorium. Timmy and A.J. are seated on one end of the stage, representing Dimmsdale Elementary School. Two other kids sit on the opposite end of the stage, they represent Snerd Elementary School. The announcer reads the first question and Timmy quickly presses the buzzer, but as he tries to answer the question, the magic wears off, and he answers "Duhh?". The Snerd Elementary kids answer correctly and go up one point. The next question, Timmy tries to answer again but then runs off, A.J. answers for him and Dimmsdale Elementary goes up a point.
Timmy goes backstage and asks Cosmo and Wanda what was going on, he didn't know anything. Cosmo says "welcome to my world" while Wanda explained to Timmy that because he is in a competition, Da Rules forbid his magic from being used. Cosmo and Wanda figured he would know that since he knows everything, but Timmy apparently did not. Back at the Brain-a-thon, Snerd leads Dimmsdale by 8 points. A.J. goes back stage and asks Timmy if he was just faking his stupidity to try a heroic comeback, but Timmy tries to make it up to A.J. for mocking him and that A.J. earned his intelligence while Timmy cheated "in an impossible to explain way". A.J. says that Timmy is good at video games, and because of this he has good reflexes on the buzzer. Timmy asks the announcer to switch chairs with A.J., and with Timmy's fast response time and A.J.'s intellect, Dimmsdale's team manages to pull back into the competition.
At the final question, Dimmsdale and Snerd Elementary are tied at 99 points. The final question is one that can be about anything, and to the surprise of them all it is a question about the video game Crash Nebula. Timmy knows he can get this one, he looks over at one of the Snerd kids, who looks down and reveals he is wearing a Crash Nebula hat. Timmy and the other kid slow motion jump toward their respective buzzers. Timmy reaches his buzzer first, and answers the question in perfect detail correctly. Dimmsdale wins, and Timmy is awarded a golden brain-shaped trophy, which he asks to go to A.J. who truly earned it. A.J. lifts the trophy up in triumph, and then promptly drops it on the ground shattering it, he says "I need to work on the gloating.". Back at home, Timmy's parents have hired a lawyer to try to come up with a response to Timmy's smart tirade to them earlier. Timmy says he deserves to be grounded and that he was a smart creep. The lawyer says Timmy figured it out all by himself, and leaves, but he still wants to be paid. Timmy's parents gloat that they grounded a smart kid, and Timmy decides there is nothing left to do but study. He then has Cosmo push away the books and they both hop back into the video game while Wanda huffs in defeat.