Timmy comes from a middle class background which is often referenced. He is arrogant and selfish and constantly wishes for things, but nonetheless, whenever his wishes go wrong, Timmy works to set things right. Despite his selfishness, Timmy is shown to be very philanthropic, which is visible when he goes out of his way to save humanity and the world. He is shown to love both his fairy godparents and his biological parents, and values their company. Timmy's English background is mentioned in the form of his ancestor Nigel P. Turner, who was an upper middle class banker in 18th century London.
It is also shown that he is trained in kung fu, as seen in "Kung Timmy" and enjoys martial arts.
Aside from his wishing habits, Timmy is shown to engage in activities that a 10-year-old normally would. He always remains the same age, regardless of the three summer vacations in the series. He is also shown to change his age due to wishes, such as in the episode "Baby Face", where he is turned into a baby to escape the wrath of Francis, a school bully. In a separate episode, he is shown as an 18-year-old. In this form, he is very muscular, with thick arms and a sleeveless pink shirt, and is significantly taller. As an adult, he is still muscular, with a white shirt, pink tie and blue pants similar to the pair he wore in his youth. In the bleak future, he wears an indigo suit with light black shoes.
Timmy longs to be popular and regularly stands up against teachers and bullies, and is not above torturing his enemies for his own amusement. He is shown to be addicted to wishing to the point that he nearly lost his resourceful and physical skills, and was required to go to "wishing rehab", where he re-learns how to rely on his own skills again. In "Fairly OddBaby", Timmy gets a fairy baby brother named Poof, whom Cosmo has instead of Wanda. In "Wishology", Timmy is revealed in the Cave Prophecy in Fairy World as the one to defeat the Darkness and its forces. In the end, Timmy becomes friends with the Darkness, who had only been wanting a friend. In "Birthday Bashed", Timmy finally celebrates his 11th birthday. (next birthday)
It is seen in "Add-a-Dad", while Timmy and his dad are playing catch, that he is left-handed. He is a claustrophobic, podophobic, and fears clowns; facts exploited by Vicky to torment him by organizing a "Barefoot Clown Orange Juggling" festival at his school.
The concept of Timmy first came from series animator Butch Hartman's idea of a male version of Cinderella who is watched over by a fairy godmother.
According to the live-action film adaptation, A Fairly Odd Movie: Grow Up, Timmy Turner!, Timmy will inexplicably manage to keep Cosmo and Wanda with him by refusing to mentally age and even staying in fifth grade despite now being 23 years old. But he will unexpectedly develop feelings for the now-gorgeous Tootie, and will be stuck having to choose between staying a child and keeping his fairies or growing up so he can be with his new love. In the end, after Cosmo, Wanda and Poof are taken captive by the evil oil tycoon Hugh J. Magnate Jr., Timmy saves their lives by confessing his love for Tootie (who has by now found out about the fairies) and passionately kissing her, thus growing up and losing his fairy family. However, because of this act and how much he loved them, the Fairy Council adds a "Timmy Turner Loophole" to "Da Rules", stating that Timmy is now allowed to keep his fairies in his adulthood, provided he make wishes for other people and not himself. Timmy and Tootie, now a couple, then start a business called "Wishful Thinking", which they use as a way of disguising Cosmo, Wanda and Poof as they grant wishes to help unfortunate people everywhere.