Corey is a supporting male character who appears in the first Pokémon movie. He is one of several skilled Pokémon Trainers who receives an invitation from the being known as Mewtwo to travel to a remote location called New Island. Very little is known about his background, including his specific hometown within the Kanto region, but his skill with a diverse team of Pokémon marks him as an accomplished Trainer. He is characterized by a confident and competitive nature. Upon arriving at the fortress on New Island, he proudly speaks about the strength and speed of his Pokémon, showing a strong belief in his own abilities as a Trainer. This confidence, however, is paired with a notable impulsiveness. He is quick to take charge in a crisis and is often the first to act, whether by launching an attack or challenging an opponent. This tendency sometimes borders on recklessness, as he does not hesitate to confront an overwhelmingly powerful foe like Mewtwo directly.

Corey's primary motivation throughout the film is to prove his strength as a Trainer. He answers Mewtwo's challenge because he believes himself worthy of facing the world's greatest Pokémon master. When he and the other guests discover that Mewtwo intends to destroy the world and rule over a planet of cloned Pokémon, his motivation shifts toward direct confrontation and resistance. He is not content to stand by and is driven to fight back against this threat, partly out of a sense of pride and partly as a defensive reaction to the danger posed to him and his Pokémon.

In the story, Corey serves as one of the elite Trainers who successfully overcome the violent storm created by Mewtwo to reach New Island. While most other invitees are turned back by the rough seas, Corey arrives by flying on the back of his powerful Pidgeot, demonstrating his resourcefulness. Once inside Mewtwo's fortress, he is present alongside fellow Trainers Ash Ketchum, Misty, Brock, Neesha, and Fergus when Mewtwo reveals its plan. He is among the first to engage the enemy, ordering his Rhyhorn to charge at Mewtwo, though the attack is easily deflected by Mewtwo's psychic powers. Later, he is the first to accept a challenge from Mewtwo's cloned Pokémon, pitting his own Venusaur, which he has nicknamed Bruteroot, against a cloned Venusaur. Bruteroot is swiftly defeated by a single Vine Whip attack. This defeat leads to Corey's entire team being captured by specialized Mewtwo Balls, after which they are cloned. He is later forced to watch from the sidelines as his original Pokémon fight against their own clones in a seemingly endless battle. In the aftermath of the climax, when Ash is turned to stone and subsequently revived, Mewtwo has a change of heart. As part of this resolution, Mewtwo erases the memories of all the human Trainers, including Corey, wiping their recollection of the events on New Island. Corey and his Pokémon are then returned safely to the harbor at Old Shore Wharf, with no memory of their ordeal.

Corey's key relationships are primarily defined by his interactions with the other Trainers. He has a clear dynamic with his peers Neesha and Fergus, acting as part of a trio of skilled and confident Trainers who stand apart from the less experienced Ash and his friends. He treats Ash with a degree of superiority, especially when showcasing his own Pokémon. His most significant, though entirely adversarial, relationship is with Mewtwo. He is one of the first humans to directly challenge the genetic Pokémon, and his defeat at the hands of the cloned Venusaur makes him an early casualty of Mewtwo's campaign. The deepest bond he displays is with his own Pokémon, particularly his starter and powerhouse, Bruteroot the Venusaur, and his loyal flyer, Pidgeot. However, his impulsive commands and overconfidence contribute directly to their capture and cloning.

In terms of development, Corey does not undergo a major emotional or philosophical change during the film. As his memory of the entire incident is erased by Mewtwo, he ultimately reverts to the same confident Trainer he was at the beginning. He does not learn from his defeat because he has no recollection of it, making his character arc a static one. The only subtle hint of development is in the film's final scene, where he joins the others in watching the sky clear, now free of the arrogance he displayed upon his arrival. However, this is more a consequence of the memory wipe resetting his state of mind than an internal realization. Outside the main film, one alternate timeline depiction in a later movie shows him competing in a high-level Pokémon League Conference, indicating that he remained a successful Trainer.

Corey's notable abilities are reflected in his team of fully evolved and powerful Pokémon, demonstrating that he is a highly competent battler. His known team consists of six diverse Pokémon: Pidgeot, Scyther, Hitmonlee, Sandslash, Rhyhorn, and his Venusaur nicknamed Bruteroot. His Pidgeot is notably fast and strong enough to fly him through a dangerous, supernatural storm, a feat not matched by many other Trainers. In battle, he is proactive and aggressive, preferring to launch the first attack as shown by his Rhyhorn's charge. Despite his team's overall strength, specific battle techniques are seldom shown. Bruteroot is seen using Razor Leaf in its duel, while Rhyhorn uses a charging move like Take Down. Ultimately, his abilities prove insufficient against the power of Mewtwo's clones, which easily overpower his team. He is a skilled Trainer capable of reaching an elite event like the invitation to New Island, but he is not in the same league as a genetically engineered legendary Pokémon.