Graduation Match: Part 1 - S1-E51
Stupidity: Zane activates the spell card Polymerization and explains that "by sending some select monsters from my hand to the grave, I can summon a Fusion monster", to which Jaden replies "To the grave?" as if he is completely surprised by the fact that the monsters will go to the grave. Jaden is completely familiar with Polymerization and has used it in nearly every duel, so he should be aware that the monsters will be sent to the graveyard when Polymerization is used. (00:07:42)
Tag Team Trial: Part 2 - S1-E11
Stupidity: After Jaden summons EH Tempest, he also activates the field spell Skyscraper. This means that Tempest gains 1000 attack points (going from 2800 to 3800) when it attacks Dark Guardian (whose attack points are 3800). Since Dark Guardian can't be destroyed by battle, Jaden sacrifices a card to keep Tempest on the field. What was Jaden expecting? He already knew about Dark Guardian's effect, and there would've been no life point damage, so this attack wouldn't have benefited him in any way.
Tag Team Trial: Part 2 - S1-E11
Stupidity: After Jaden summons Elemental Hero Sparkman to the field, he also activates the spell card Spark Blaster, which he equips to Sparkman so that it can change any monster on the field in attack mode to defence mode. He decides to switch Gate Guardian to defence mode, however, he could have also switched Defence Wall to attack mode as well. Then he would've been able to have Sparkman attack Defence Wall, and it would have been destroyed since it has 0 attack points.
Tag Team Trial: Part 1 - S1-E10
Stupidity: Para uses a spell to summon Suijin (2500 ATK), he sacrifices Kaiser Seahorse to summon Sanga of the Thunder (2500 ATK). Then sacrifices those two monsters, along with Kazejin (2400 ATK) to summon Gate Guardian (3750 ATK). He then has Gate Guardian attack Steam Gyroid causing Syrus to lose 1550 points. But if he had attacked Steam Gyroid with one of the monsters he already summoned, then attacked directly with the other, Syrus and Jaden would have lost significantly more life points.
Duel Distractions: Part 1 - S1-E36
Stupidity: When Bastion shouts during the duelling exercise, Syrus and Chumley fall over and drop their cards. About 15 seconds later, Chumley stands back up, but leaves some of his cards scattered on the floor. First, his cards could have got dirty or damaged, so Chumley deciding to leave them on the ground is very foolish. Second, Bastion doesn't seem bothered that the cards are still on the ground, despite the whole point of the exercise is about being ready for duelling. (00:04:05)
Stupidity: When Crowler goes into the chicken coop, he leaves the door to the coop wide open. Leaving the door open could have risked the chance of the chickens running out of the coop. (00:00:20)
Stupidity: When Jaden is preparing for the school duel, Syrus, Chumley, Alexis and Bastion approach him with cards that he could use for the duel. Syrus offers Power Bond, however, this card can only summon Machine-type Fusion monsters, and Jaden doesn't have any Machine-type Fusion monsters in his deck, making this card useless to him. (00:03:07)
