Unleash the Dragon: Part 2 - S3-E26
Revealing mistake: When Marcel activates Dimension Fusion Destruction, whilst explaining that by removing the three Sacred Beasts from play, he can summon a new monster, there is a shot of him saying "I can summon Chaos Phantasm Armityle." Right at the start of this shot, a minor animation error occurs where part of his hair suddenly becomes more shadowed partway into the shot. (00:14:25)