The Real Reason Pokémon Replaced Brock Is Hard to Believe Because Nobody Saw It Coming

As the longest-lasting of Ash's companions, Brock is a fixture of the Pokémonanime. He traveled with Ash through Kanto, Johto, Hoenn, and Sinnoh, and later made appearances in Alola and in Journeys. But Brock was actually the first of Ash's companions to leave the show--so what led to his sudden departure, and equally sudden return?