Gary was born and raised in Kanto by his mother and sister in Pallet Town, before going on his own journey through the region with a Totodile alone, defeating 8 Gym Leaders, making it to the Indigo League and defeating the Elite Four and Lance, before becoming the Champion himself. He was defeated by his best friend shortly after becoming Champion and departed the role. Following this, he went on a journey to other regions.
The Alexis Saga
Gary first appeared in An Intellectual Meeting! after helping Alexis retrieve a stolen item from Bill. He then joined Alexis in meeting Professor Oak, who he revealed to be his grandfather. When they met him, both received Starter Pokémon, with Gary getting a Bulbasaur. He and Alexis then battled (in which he won) before deciding to join her in her quest for Celio and Bill.
After battling against a Biker Gang and rescuing little girl Lostelle, he decided to stay longside Greta and Morty throughout Alexis' journey through the Sevii Islands, capturing a Gastly and Klink along the way.
It was discovered while travelling that Gary had in fact lost his title of Champion before coming to the Sevii Islands, wanting to tell his grandfather before Alexis turned up. He decided not to continue his fight for the title, and instead, continued to travel.
Upon traveling to Unova with Alexis, Gary eventually left the group to take a fishing job in Hoenn. However, it was mentioned that he left the job soon after and returned to Kanto.
He reappeared during the events of M03 and M04 to help Alexis take down the Ghetsis Initiative.