Plot hole: Timmy uses his heat vision, that he previously wished for, to win the race for his future dad. But it's revealed later in "Smarty Pants" that if you use a previous wish in a contest, it is magically taken away because it's cheating.
Factual error: In Deja Vu, after Vicky steals Timmy's Cosmo watch, she redoes the time to when it was after school. Vicky redoes the time so that a million cats appear to torture Timmy. They throw him out a window which really has solid glass and no sliding doors. He should have been hit onto the window.
Continuity mistake: In 'The Grass...,' when Timmy is juggling a bear, the bear wrestler, and the lead carny, there is a close-up of the lead carny as he flies past the camera over and over, yet you never see the bear or the bear wrestler fly past the camera.
Continuity mistake: Episode 66-5 "Hassle In The Castle/Remy Rides Again": In the final scene, notice the house across the street furthest to the left; first time it is shown there is a large window with light coming through. The last time we see the same shot, however, it is a totally different house.
Continuity mistake: In the scene when the Sleep Fairy shrinks while talking to Timmy, he measures himself. The ruler says three inches. Then he shrinks down to two inches. The camera cuts to Timmy. Then it cuts back to the Sleep Fairy, who quickly discards the ruler. If you are fast enough, you'll notice that the ruler says he is three inches again.
Continuity mistake: Beddy Bye- In an early scene, Timmy's parents are watching "Up Late in Dimmsdale." In a later scene, when Timmy is featured on the show after they've run out of guests, the sign behind him is "Late Night in Dimmsdale" instead of "Up Late in Dimmsdale" like it was before.
Continuity mistake: Episode 4-6 "The Jimmy Timmy Power Hour": In the scene where Timmy and Cindy are in the Candy Bar their milkshake has two straws for the first two shots. But in the next shot there's only one straw which is on Timmy's side, it then moves to Cindy's side. Then when Carl, Sheen, and Libby run in both straws appear again. When they all run out there's only one straw and on Timmy's side.