After assuming a human form in Pokémon Pokopia, Ditto meets Tangrowth.
The Tangrowth is known as Professor Tangrowth and has taken responsibility for studying the damaged environment. This meeting establishes the game’s central partnership: Ditto helps rebuild habitats while Professor Tangrowth investigates why humans and Pokémon left.
The story begins after Ditto finds its trainer’s old Pokédex and uses it as the basis for its human-like form. It later encounters a dehydrated Squirtle and begins restoring habitats so Pokémon can return to the area.
Tangrowth is sometimes confused with other Grass-type Pokémon because Pokopia features environmental restoration and plant growth. However, Professor Tangrowth is the specific character Ditto meets after taking human form.