Bill

In the Pokémon anime (specifically the original series, "Pokémon: The Beginning"), Bill is a friendly and knowledgeable Pokémon researcher who lives in a lighthouse (referred to as Bill's Lighthouse) along the coast near Cerulean City.

He's portrayed as nice, curious, and an out-of-the-box thinker. Professor Oak describes him as someone who knows even more about Pokémon than Oak himself. In his sole major appearance (Episode 13: "Mystery at the Lighthouse"), Ash, Misty, and Brock stay at his place on Oak's recommendation.

Bill is eagerly waiting to observe and identify a mysterious, giant Pokémon (implied to be a massive Dragonite) that occasionally appears offshore. He's accidentally stuck inside a realistic Kabuto costume (which he wears for research purposes) when the group first meets him, and they help free him.

Unlike his game counterpart—who's famous for inventing the Pokémon Storage System and famously gets fused with a Pokémon— the anime version focuses more on his role as a dedicated researcher and observer of rare Pokémon phenomena. He doesn't appear much beyond that episode.