Stupidity: When Mac and Lindsay are reconstructing the stab wound found on their victim on their pig specimen, a couple of the weapons they use are long, thin knives; since they obviously don't match the circular wound, Mac at the very least would know those could be excluded by default.
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)