TV-Series
Description
Gary Oak is a prominent recurring character in the Pokémon anime, originating from the Kanto region's Pallet Town. He is the grandson of the renowned Professor Samuel Oak, a position that initially fuels a deep sense of pride and confidence in his abilities as a Pokémon Trainer.

At the outset of his journey, which he begins at age ten alongside his neighbor and childhood friend, Ash Ketchum, Gary is defined by his arrogant and boastful personality. He is highly skilled and knowledgeable, a fact he never hesitates to demonstrate, often at Ash's expense. His early approach to training is characterized by a focus on power and strength, favoring Pokémon with great physical force. He travels in a distinctive red sports car accompanied by a group of cheering supporters and is known for his catchphrase-esque taunts, which serve to constantly challenge and motivate his rival.

Despite his brash exterior, Gary is a remarkably competent and strategic battler. During his initial journey through Kanto, he amassed ten Gym Badges, a notable achievement that highlights his talent. His skill carried him to the 32nd place in the Indigo Plateau Conference. He continued to prove his strength in the Johto region, reaching the 16th place in the Silver Conference. His team in these early days was formidable, including powerful Pokémon such as Nidoking, Arcanine, and ultimately a fully evolved Blastoise as his starter.

Gary's defining characteristic is his significant character development. A pivotal turning point occurs during the Silver Conference, where he faces Ash in a full six-on-six battle. Ash's victory serves as a humbling experience that prompts Gary to reevaluate his path. Following his travels in Johto, Gary makes the mature decision to retire from being a full-time Pokémon Trainer and instead pursues a career as a Pokémon Researcher, following in his grandfather's footsteps. This shift marks a profound change in his personality; the arrogant rival transforms into a calmer, more mature, and respectful individual.

As a researcher, Gary dedicates himself to uncovering the mysteries of Pokémon, with a particular interest in fossil Pokémon and evolution. He is shown working at labs, such as on Sayda Island where he successfully revives an Aerodactyl from an Old Amber. He later moves to the Sinnoh region to assist Professor Rowan, where his new, more thoughtful nature is fully displayed. There, he takes on a protective, older brother-like role, particularly towards younger trainers, and works to defend rare Pokémon from poachers like Pokémon Hunter J.

The relationship between Gary and Ash evolves dramatically over the course of the series. What begins as a one-sided, often bitter rivalry deepens into a mutual respect and a genuine friendship. A powerful symbol of their bond is a broken Poké Ball, one half of which each carries as a reminder of their shared past and their promise to meet again. Gary often serves as a catalyst for Ash's growth, and his own journey from a boastful prodigy to a dedicated scientist provides a counterpoint to Ash's continued pursuit of becoming a Pokémon Master. His notable abilities transition from being a top-tier battler to a skilled researcher, though he remains a powerful trainer, as seen when he battles Ash with his Electivire. In later series, he continues his research as part of the ambitious Project Mew, further showcasing his dedication to the scientific study of Pokémon.