He is a white-haired man who pulls Edward Elric into his makeshift clinic when he sees Ed's automail hand. He immediately slams Ed onto a stool and starts demanding to know who Ed's engineer is, as he pushes Ed's coat sleeve back to see all he can. Although Ed is put off by being treated like an object attached to the automail, he grows fond of Gonzales, nicknaming him Gramps and wishing him well.
Ed encounters Gonzales later after he and Al start heading up to Table City, arriving in time to see a funeral service being held for Pedro, who died while looking for Julia with Ed. The funeral is also being held for two children that Julia had taught in her school, and a woman who died in childbirth as well as her dead baby.
Ed meets Gonzales again after he and Winry have sought him out, as Ed's arm needs a gear. Gonzales is delighted to meet the young engineer, and after Winry installs the gear, Ed leaves Winry with Gonzales. Ed's final encounter with Gonzales is after the fight for Table City has ended, when he is standing with a large group of citizens from the valley. He is last seen giving an automail leg to Julia, who had lost her original one saving her brother. Gonzales is a generous man, installing automail to help Milosians who have been wounded while working for their Cretan military, who is still present and demanding their service, as the valley still belongs to Creta. Gonzales tells his patients to pay him when they can. Like the engineers Ed encounters in Rush Valley, he shows the same enthusiasm for new techniques in automail, with his eagerness for his craft overcoming manners or the discomfort of the person with the automail. He also defends Ed and Al at the funeral service when other Milosians try to attack Ed due to his Amestrian heritage, explaining that Ed and Al aren't like their oppressors.