While Ash was preparing for the Pokemon League in Kanto, he discovered that Bruno was training in the mountains near Pallet Town. Enthusiastic about meeting Bruno, Brock and Misty set off towards the mountains. It was said in the local region that Onix grew much larger than usual in these mountains.
After Bruno saved them from a giant Onix, Ash and Brock begged to become his students. Bruno agreed, provided they followed all of his commands without question. Bruno had them perform various tasks such as chopping wood, carrying water, and carving chopsticks - among other duties. Misty began to suspect that Bruno was not what he seemed.
Brock decided to prove how incredible Bruno was by surprising him with a sneak attack. He believed that Brunos reflexes would be so impressive; they would easily stop Brock in his tracks. However, Brock nearly knocked Bruno unconscious instead. Bruno admitted that he did not possess any secret techniques for training Pokemon and merely required someone to perform menial tasks for him.
Later, the children were once again pursued by a giant Onix. Bruno managed to calm the enormous Pokémon, which then decided to join his team. Bruno declared that the true secret behind successful Pokémon training involves caring for both Trainers and their creatures.
In the anime, Bruno possesses incredible physical strength and agility, which he uses with almost superhuman expertise.