Jim Cook

Jim is an expert geologist and archaeologist, having taken part in an excavation of a Tyrannosaurus in the past, and has a crocodile named Shirley(in original version: Karen), initially believed to be a fake by Vellian Crowler and Bonaparte, who he carries around in a specially made backpack wherever he goes. Jim regards Shirley as "family," and does not consider her a pet. He places great trust into Shirley and often uses her as a judge of good character, which started his friendship with Jaden Yuki. Jim wields a Duel Disk in the shape of a boomerang. After saving Shirley from an animal trap, Jim injures his right eye.

After regaining consciousness, he is imbued with the Eye of Orichalcum by a man touched by Jim's devotion to Shirley. The man who gave it to Jim told him it was supposed to have incredible powers when in the presence of a special comet. Afterwards, he keeps his right eye bandaged. During the Duel between Jaden and Axel, Shirley began acting strangely due to electromagnetic waves coming from within the jungle. Meeting up with Jaden and his friends after Shirley inadvertently attacks Tyranno Hassleberry the next day, he and the group venture deep into the woods to investigate.

Seeing another opportunity to claim duel energy, Professor Viper reactivates the signals, causing Tyranno to act wildly and face Jim in a Survival Duel. Tyranno quickly regains his senses and lashes out at Jim for disturbing his dinosaur monsters, but is eventually defeated. After Viper's defeat, Jim is one of the few students that aren't turned into zombies when the academy is transported into the desert. Jim accompanies Jaden and co. to an alternate dimension and assists them in defending Duel Academy from zombified students. After their journey into a third alternate world, Austin and Jim face Jaden, who has turned evil and begun calling himself the "Supreme King".