Bruno first showed up in To Master the Onixpected!, though he might've had an earlier appearance in Pokémon - I Choose You! as a mysterious Trainer with Nidorino and Onix. He's voiced by Maddie Blaustein in English and Toshiyuki Morikawa in Japanese.
When Ash was gearing up for the Kanto League, he learned that Bruno was training in the mountains near Pallet Town. Brock got excited about meeting him, so the group headed out with Misty in tow. The area was famous for hosting unusually huge Onix.
After Bruno rescued them from one of these giant Onix, both Ash and Brock wanted him to train them. He agreed—but only if they'd follow his orders completely. What followed was a lot of grunt work: chopping wood, hauling water, carving chopsticks. Misty pretty quickly decided Bruno was running a scam.
Brock wasn't convinced and tried to prove Bruno's skill by launching a sneak attack. He figured Bruno's reflexes would be incredible and he'd stop Brock without breaking a sweat. Instead, Brock nearly knocked Bruno out cold. That's when Bruno admitted the truth: he had no secret training methods and basically just wanted free labor.
Things shifted when a giant Onix chased them again. This time Bruno managed to calm the massive Pokémon down, and it ended up joining his team. That's when Bruno revealed what actually mattered in training: Trainers and Pokémon caring for each other.
Bruno's got incredible physical strength and speed in the show, moving with almost superhuman precision.
Content compiled by AnimeList.moe from publicly available sources.
