The Fairly OddParents S03E23 - Mind Over Magic

Timmy, tired of Mr. Crocker's constant pop quizzes (in which he asks a question that no one can answer, or does not give enough time for people to answer), which everyone fails, wishes that he had mind reading powers. He uses this to pass Crocker's pop quizzes and mess with his friends' heads. Unfortunately, Crocker figures his wish out, and uses an anti-mind reading helmet (which causes someone trying to read the mind of the wearer to read their own mind instead) as part of a new plot to capture his fairies.