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.
Homecoming Duel: Part 2 - S2-E16
Stupidity: Jaden uses the power of contact fusion to fuse Elemental Hero Neos and Neo-Spacian Flare Scarab to summon Elemental Hero Flare Neos without Polymerization. Aster shouts "That's against the rules", but in the previous episode, he saw Jaden summon Elemental Hero Aqua Neos in the exact same way, so he should be aware of this. Or at the very least, this shouldn't be a surprise to him. (00:15:05)