The foreman is a one-off character from the episode "Dig Those Diglett!" He never gets a proper name, though that's what everyone calls him—including the official Pokémon.com summary. In the English dub, he's got a pretty distinct Eastern European accent.
The guy's frustrated because Diglett keep wrecking the Gaiva Dam construction project, so he puts out a call for Trainers across Kanto to help deal with them. The reward? A relaxing stay at a hot spring. Gary answers the call, but Ash and his crew show up uninvited along with Team Rocket, and they all volunteer to help anyway. Problem is, when the recruited Trainers try to actually battle, their Pokémon just immediately return to their Poké Balls. Even Pikachu won't fight. The foreman's already irritated, and this just makes things worse.
That night, he watches the Diglett and Dugtrio working to keep the ecosystem balanced, and it clicks for him—the dam would destroy all that and basically make the whole area uninhabitable for everything living there. He calls off the project and decides to leave the forest untouched. Sometimes you need to see things from the Pokémon's perspective.
Content compiled by AnimeList.moe from publicly available sources.
