Timmy has the same hairstyle as Cosmo, Vicky (other than the ponytail) and Danny Fenton from Danny Phantom.
In the original concept, Timmy's hat was intended to be blue, but because Butch Hartman's blue marker had run out of ink, Timmy's hat became pink instead.
His trademark pink hat is due to his parents expecting a girl. 
Timmy has his own theme song.
Timmy's full name is Timothy Tiberius Turner.
Timmy is named after Butch Hartman's younger brother, Timmy Hartman.
Timmy's birthday is March 21, which makes him an Aries in the horoscope.
Timmy's hair was originally intended to be red, but his hair color was dyed so it wouldn't match Vicky's.
In the pilot episode, The Fairly Odd Parents!, his hair was dark red instead of its usual light brown. Beginning in Too Many Timmys!, his hair was light brown like it would be for the rest of the series.
Timmy can burp the alphabet.
Grandpa babysitting Timmy when he was an infant, is indirectly responsible for Timmy's buck teeth (due to Pappy letting him suck on a pacifier for too long in The Good Old Days!).
Timmy is allergic to oranges and sauerkraut.
Timmy Turner has only gotten A's on his tests five times. When he got an A+ in "Cosmo Con," his friends started screaming as they thought the world was coming to an end (he got an A+ due to his short attention span and him doodling).
When the Oh Yeah! Cartoons shorts are reused in later episodes, Timmy's voice is redubbed using his current voice actress (Tara Strong); this may be to due to continuity, since Strong's voice sounds a bit different than Bergman's.
Timmy has shown many symptoms of Attention Deficit Hyperactivity Disorder (ADHD). These include: Major focusing problems (even admitted a few times in the series), hyperactivity (not counting his sugar rush in Just Desserts!), antisocial behavior (he only has two friends, not including his "back up friends"), forgets what he is doing occasionally, and even goes to therapy (usually having to deal with social problems). He is also great at finding things, and brain scans and studies of ADHD show that those who have it show more "hunter-gatherer" traits.
He appeared in the Big Time Rush episode, Big Time Cartoon.
According to Cosmo, Timmy Turner weighs 50 lbs. without his buck teeth, but 77 Secrets of The Fairly OddParents Revealed! shows that Timmy weighs 60 lbs. with his buck teeth. So, that means Timmy's buck teeth weigh 10 lbs. In the Oh Yeah! Cartoons short "Too Many Timmys!, Timmy says that he's 45 lbs., all muscle
Saying "What could possibly go wrong!" before a disaster
Whenever people would ask where he got the stuff he wished for he would tell them "Uh..Internet?"
In Abra-Catastrophe! Timmy is shown when he was young not having fully-formed buck teeth, but in every episode to feature Timmy as a baby (not including The "Good Old Days!", Although it does explain him getting his buck teeth), he has his buck teeth.