Corrected entry: In the Season 4 episode "Mr Right", Timmy wishes that he was always right, and the magic makes it so that anything he says automatically becomes true. When he goes to tell Vicky he has fairy godparents, he actually says, "You'll probably be so busy that you won't listen to me," which Vicky refutes by telling Timmy that she's not only going to listen, but going to videotape him. But since he said that she wouldn't listen to him, the magic should have made that statement true and Vicky wouldn't have listened to him.
Corrected entry: In the episode where Timmy and Mark, the tentacled-alien from Yugopotamia, fight for Vicky, in what Mark calls "the Digifat", in the first round at the arena, Timmy wishes to be a robot, but turns out to be a pillow-shooter. But it has been specified more than once that Timmy can't wish to help him win a competition.
Corrected entry: On Wanda finally returns from her day off, she sees Timmy and Cosmo playing cards and trying to not let her know about the "World Domination." When Cosmo makes the walls fall down, you only see the walls that fell down, no roof. And since there wasn't a roof, surely she would have found out by looking up and seeing the Martians.
Corrected entry: When Vicky turns nice, she does nice things for Timmy, including placing a thermometer in his mouth - with the bulb outside the mouth. The bulb, which has heat sensitive mercury, should always be placed inside the mouth, in order to take a person's temperature.
Corrected entry: When Timmy is in that crazy day-care place, Gary and Betty say that he can't go home until Vicky comes back. If Timmy's parents were just going on a trip, and since there was no indication of how long Vicky was going to "Europe", shouldn't they take him home later? And if Timmy can wish himself onto the alien planet Yugopotamia, why shouldn't he just wish himself home?