Awakening of Evil: Part 2 - S2-E38
Stupidity: When Odion activates Swords of Revealing Light (preventing Joey from attacking for three turns), Joey switches all of his monsters to defence mode. There was no real benefit to this as Odion had no monsters on his side of the field and Jinzo was less powerful in defence mode, having only 1500 defence points, compared to 2400 attack points.
Let the Finals Begin! - S2-E32
Stupidity: Kaiba boards the blimp and tells his aides to begin take-off immediately because "the Egyptian God cards are already on board" despite only seven out of eight duelists being on board (before Ishizu arrives at the last second). However, this contradicts how the duels are set up. The finals are played with each of the eight duelists facing off against each other in four separate two-player duels. If one of the players was not included, this would have messed up the Battle City finals completely. (00:09:17)
Legendary Fisherman: Part 1 - S2-E19
Stupidity: When Kaiba attacks the hunters with Obelisk the Tormentor and destroys their two face-down monsters, the tall hunter activates his face-down card Mirror Force, a trap card that can destroy any attack position monster on the opponent's side of the field during an attack (before finding out the trap card won't work with this monster). Technically, the hunter could've activated this card before their two face-down monster cards were destroyed instead of after. (00:06:17)
