Tangrowth is the lone resident Ditto meets at the start of Pokémon Pokopia.
When Ditto awakens in the Withered Wasteland, the world has become barren and the humans are gone. Tangrowth is described as the only remaining resident in that devastated area and lives alone among the ruins.
Tangrowth later becomes known as Professor Tangrowth. This character helps introduce the setting and explains that humans and other Pokémon disappeared long ago, although he does not know where they went.
The meeting establishes the game’s central goal: restoring habitats so that Pokémon return to the ruined world. As Ditto repairs the environment and attracts more Pokémon, Tangrowth’s hope that humans might eventually return also grows.