In *One Piece: Mega Mecha Soldier of Karakuri Castle*, Tony Tony Chopper joins the Straw Hat Pirates' treasure hunt on Mecha Island. During the adventure, a mysterious voice repeatedly calls out to Chopper. Compelled by these calls, he separates from the main group to follow them. This voice originates from the island itself, revealed to be a giant ancient turtle. Chopper communicates with the turtle and learns it awakens every 1,000 years to lay its eggs—a process integral to the island's riddle and the film's central conflict. His ability to understand the turtle arises from his inherent reindeer nature combined with the effects of the Human-Human Fruit, enabling this interspecies communication.