Action Packed / Smarty Pants - S2-E4
Corrected entry: In Smarty Pants, Timmy can't be smart enough to win the Brain-A-Thon, it doesn't make sense because he didn't directly wish to win. Plus Chester could still be good in Foul Balled so Timmy should be able to be smart.
Correction: According to the rules, it is also forbidden to use magic to win contests and use a previous wish in a contest. This is also stated in "Hex Games." Whenever in other episodes where Timmy uses magic from a previous wish to win, it's a mistake. Clearly, the writers never established the no equipping yourself to win rule until later episodes. Equipping yourself to win is almost the same as directly wishing to win. This is why in "Hex Games", Timmy was forbidden to equip himself to win. Frankly, this point is highly debated.