The player's starter Pokémon in these games is a special Pikachu or Eevee commonly referred to by the game as a Partner Pokémon. Players of Let's Go, Pikachu! start with Pikachu, while players of Let's Go, Eevee! start with Eevee. These Partner Pokémon have a fixed 31 IVs in every stat and have higher base stats than normal Pikachu and Eevee, but cannot be Shiny. Their gender is determined when the player starts a new game, as it is seen in a cutscene before being added to the party.
There are two set encounters with Snorlax accessible via the Poké Flute; one on Route 12 and one on Route 16. The player must capture or defeat at least one of them to proceed to Fuchsia City. Unlike most encounters in the game, the player must defeat Snorlax in a battle with a strict time limit of five minutes before they have the chance to capture it. The Snorlax on Route 16 will receive a boost in Defense at the start of battle, while the one on Route 12 receives a boost to Attack, similar to a Totem Pokémon or Ultra Beast.
The four fake item balls in the Power Plant all lead to traditional battles with wild Electrode with a time limit of five minutes. If the player can defeat them, they have an opportunity to capture them.
Unlike most encounters in the game, the player must defeat the Legendary birds in a battle with a strict time limit of five minutes before they have the chance to capture it. The birds will receive a boost to all of their stats at the start of battle.
After successfully capturing one of the birds, the player may encounter others of the same species as rare spawns.