Thomas "Tom" Sawyer is the main antagonist of the full length special episode, "Shelf Life".
Tom is the title character of The Adventures of Tom Sawyer, a mischievous and imaginative boy not unlike Timmy. Thrust into the 21st century, he quickly takes an affinity to monster trucks and rock music as is stereotypical of Missourians. Unlike his usual fictional appearances however, Tom Sawyer is a villain in The Fairly OddParents who tricks Timmy and his fairies, and nearly destroys the universe by attempting to alter the book of astrophysics. He is driven to do so by his desperation to escape life in Missouri.
He has black hair, wears blue overalls, and wears a straw hat. He also has light blue eyes, freckles, and a missing tooth. He speaks with a rural Southern accent. Despite being nearly the same age as Timmy, Tom is much taller than him.
After finding out that he is a fictional character in a story that never changes, Tom Sawyer tricked Cosmo into giving him his wand which he used to wish himself into other books. While in the books, Tom goes around the stories and creates changes to the books' titles and storylines. This causes general mischief for Timmy and his fairies, who were trying to track him down and retrieve Cosmo's wand before he reached the last book in his path, "Astrophysics for Morons". If Tom had altered this book, it would have also altered the laws of physics in the real world (thus throwing everything into chaos).
Timmy wished for "The Rat in Spats" children's book to be placed on top of the Astrophysics book to impede Tom's progress, and then tricked Tom into a frowning competition by offering up Wanda's wand. Tom "won" the frowning contest (because frowning is Missouri's state sport as Tom claimed), but this attracted the attention of The Rat in Spats. The Rat in Spats then stated to all of them the only law in Spatsville was "You cannot ever frown."
Tom Sawyer foolishly made the error of making fun of the Rat's spats, angering the Rat greatly and in turn got stepped on by his shoe. Cosmo retrieved his wand shortly after Tom was squished. Tom yelled they haven't seen the last of him, but Timmy alters the story so that Tom Sawyer would be returned to Missouri in his storybook. Tom Sawyer was sucked back into the book and was not seen in The Fairly OddParents again. As he had altered most of the books that Timmy's friends were using for their reports, Timmy used this to get everyone else in his class to fail and have his report the only one to pass.
- It is unknown why he is not part of Imaginary Gary's group on the Unwish Island in the episode "Escape From Unwish Island".