Complex sentence: Cloyster appears in "Pokémon Pinball" as a part of the "Blue field", and a miniature Cloyster sits in the left pocket; it is part of the process of evolving a Pokémon that the player has caught.
Split into simpler sentences: Cloyster appears in "Pokémon Pinball" as a part of the "Blue field". A miniature Cloyster sits in the left pocket; it is part of the process of evolving a Pokémon that the player has caught.