Timmy has the entire summer vacation to write a long "book report" assignment. He is busy with books... but does not read any until it is almost the first day of school. Timmy wishes that Tom Sawyer would come out of the book and help him write his book report. Tom, who is lazy and arrogant, makes a deal to get Cosmo's wand. At first he enjoys the laziness, but when Timmy tries to get the wand back, Tom starts going through several (well known) books and messes with them. Timmy, Cosmo, and Wanda must stop Tom and get Cosmo’s wand back before Tom reaches the book "Astrophysics for Morons” and rewrites the law of physics!
The episode begins on the last day of the school-year. Mr. Crocker assigns the students to write a book report during the summer, despite summer vacation being the time for rest, relaxation, fun and excitement. Timmy says that he will not delay doing the assignment until the last minute... but he does not write until the end of vacation is near. Then they go to the library. His first wish is for Sherlock Holmes to come out of his book.
When Sherlock appears, he refers to Timmy by name. Timmy asks how he knows? Sherlock replies that being a detective is his job. Timmy then requests him to write his book report. Sherlock refuses because he is "a detective not a babysitter." Then Sherlock leaves. Timmy wishes for Tom Sawyer to come out of his book. Tom makes a deal with Cosmo who gives him the wand.
Timmy demands the wand back but Tom escapes into Moby Dick. The trio chases after Tom. Tom changes it to "Moby Duck" which is a giant rubber duck. Then Tom jumps into a second book: Frankenstein. The villagers almost attack Timmy so he changes by editing the words "Villagers attack" to become "The ill attack." Now the attackers are ill and there is no danger. Then, a Frankenstein "Monster...Truck" chases them. Then, Timmy changes the title from "Truck" to "Monk". Next, Tom changes "Monk" to "Hunk", which distracts Wanda from going after Tom with Timmy and Cosmo, until Cosmo changes "Hunk" to "Skunk" which sprays Wanda.
The third book is Tarzan: Lord of the Apes, in which the title character of the book (in drapes) tells Cosmo who dressed him. Then, Timmy changes "Drapes" to "Shapes". Then, the title character in the book now calls himself "Lord of Shapes" and draws a circle, a square and a triangle on a chalkboard. The 4th book is The Three Musketeers, but Tom had changed them into "The Three Mouseketeers". The 5th book is Jason and the Argonauts, in which they fight a creature before Tom changes it from "Argonauts" to "Pussycats", resulting in them singing a song to battle the cyclops. At this point, Timmy and his fairies realize that Tom is going down the row of books Wanda poofed up for Timmy earlier. Timmy realizes the final book in that row is Astrophysics for Morons and if Tom changes things in that book it will rewrite the laws of physics such as turning "gravity" into "gravy" and "planets" into "plants".
Timmy then wishes that they were in "The Rat in Spats" and that the said book would be on top of the "Astrophysics for Morons" book. Timmy and his fairies arrive before Tom, much to the latter's unhappiness. Timmy then challenges Tom to a frowning contest with the winner getting two wands. Tom then makes the biggest frown he can make since "frowning is the state sport" in Missouri. Tom tells Timmy to beat that, but Timmy says he doesn't have to. The Rat in Spats then appears and explains to the characters that in Spatsville there is only one law: You cannot ever frown. Tom doesn't believe this and starts making fun of the Rat. As Tom is laughing, Timmy then goads the Rat even more by asking him if he is going to take that insult from a punk from Missouri. The Rat screams at Tom: "WHAT DID YOU SAY ABOUT MY SHOES, PUNK?". He then proceeds to squish Tom with his foot. This causes Tom to drop Cosmo's wand, which Cosmo then retrieves. Timmy then reveals that he knew how the story went and by having Tom make fun of the Rat it led to a very big splat.
Tom, now flattened, swears at Timmy that he hasn't seen the last of him, but Timmy changes Tom's quote from "You ain't seen the last of me!" to "You're sending me to Missouri?" and Tom gets sent back to his book. The book jumps back on the shelf. Wanda suggests that they should revert the books to normal, but Timmy states they shouldn't do so just yet. On the 1st day of school, Crocker says that he graded his class's book reports quickly because they are all horrible. He gives AJ an F because there is no whale in the story of Moby Duck and also gives Sanjay an F for not discussing the musical element of Jason and the Pussycats. Crocker reveals that Timmy's report, Who Would Win in a Fight: Tom Sawyer or the Rat in Spats, was perfect compared to everyone else's reports and while he hates Timmy, he has no choice but to give Timmy an A+. Wanda realizes they forgot something, which was to wish Sherlock Holmes back into his book again. It turns out that Sherlock Holmes was with Mr. and Mrs. Turner.