Keith's Machinations, Part 1 - S1-E31
Continuity mistake: Just after Metalzoa is destroyed, when Joey says "Not bad, huh, I only wish you could've seen the look on your face when that Metalzoa of yours gets shish-kebabed," he has three cards in his hand. Then on Joey's next turn, he places a trap card face down, then summons a monster card (both of which were cards from his hand), but when Joey and Keith's life point counts are shown after Keith's next turn, there are at least four cards in Joey's hand. (00:16:03 - 00:17:49)