"As they say in Missouri, 'I ain't goin' back to Missouri!'"
— Tom Sawyer
Shelf Life is the third episode of Season 4. It is a half-hour special.
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 his 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 wants to get the wand back, Tom goes into a few (well known) books. He even changes them because they are too boring. Timmy, Cosmo and Wanda follow him into the book and chase him from book to book while Tom messes with each book he visits. Timmy, Cosmo, and Wanda must stop Tom and send him back to the correct book before Tom re-writes the laws of physics in the book "Astrophysics for Morons”! How will Timmy get the books back to normal?
The episode begins with the last day of the school-year. The teacher assigns the students to write a book report during the summer, despite summer vacation being the time for rest, relaxation, fun and excitement. Timmy said 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. (He will go to Timmy's house.) Timmy wishes that Tom Sawyer should 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 a book named "Moby Dick". The trio chases after Tom. Tom changed it to "Moby Duck" which is like a rubber duck. Then Tom jumps into a second book named "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 Wanda enjoys gazing at, until Cosmo changes to Hunk to Skunk.
The third book is Tarzan: Lord of the Apes 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" which he draws a circle,a square and a triangle on a chalkboard. The 4th book is The Three Musketeers which Wanda tries to say "The Three Mouseketeers". The 5th book was Jason and the Argonauts which they fight a creature before Tom changes it from "Argonauts" to "Pussycats" which then titled "Jason and the Pussycats" which the song starts they are trying to stop Tom before he reaches a physics book and rewrites 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. 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 that 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 "Your Sending Me To Missouri?" and Tom gets sent back to his book. The book jumps back the shelf. Wanda suggests that they should revert the books to normal. The 1st day of school began, Crocker says that he graded their book report quickly that's because they are all horrible, he gives AJ an F- for there is no such thing as Moby Dick and there is no whale in this story, he gives Sanjay an F- on his book report for not discussing Jason and the Pussycats and their musical element, he gives Timmy Turner an A+ on his book report for defeating Tom Sawyer in The Rat in Spats. Timmy realizes he forgot something which was wishing Sherlock Holmes to be in his book again. To which the camera pans that Sherlock Holmes was with Mr and Mrs Turner.