In Pokémon Diamond, Pearl, Brilliant Diamond and Shining Pearl, when two Starly attack the player and rival at Lake Verity, to which they travel upon hearing reports of a red Gyarados, they will choose between Turtwig, Chimchar, or Piplup from Professor Rowan's briefcase, which he left at the lake. In Pokémon Ruby and Sapphire, Emerald, Omega Ruby and Alpha Sapphire, after Professor Birch is rescued from a Poochyena R S OR AS or Zigzagoon E, he allows the player to keep the Pokémon they chose to rescue him with the choice between Treecko, Torchic, or Mudkip. Pseudo-rival Ethan/ Lyra only (HG/SS only) Marill In Pokémon Gold, Silver, Crystal, HeartGold, and SoulSilver, Professor Elm will have an errand for the player to run, and will give them the choice between Chikorita, Cyndaquil, or Totodile for protection on this errand, which they will then keep after completion. The Partner Pikachu and Eevee can be either gender, have higher base stats, learn Secret Techniques and have access to exclusive moves that normal Pikachu and Eevee do not. These Pikachu and Eevee are considered special, separate forms commonly referred to by the game as Partner Pokémon because they follow you. In Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!, players will start with Pikachu or Eevee, depending on which version of the game they are playing.
In Pokémon Yellow, due to being based on the anime, Oak instead gives out Pikachu to the player while the player's rival will receive an Eevee. Yellow Version and Pokémon: Let's Go, Pikachu!/ Pokémon: Let's Go, Eevee!
In Pokémon Red, Green, Blue, FireRed, and LeafGreen, Professor Oak will bring Trainers to his lab to give them the choice between Bulbasaur, Charmander, or Squirtle to begin their journey. It is also said that the starter Pokémon are extremely rare in the wild, giving the player a good reason why the Pokémon not chosen can't be found in the wild. At least one of the player's rivals will also always choose or have a starter Pokémon, typically the one that has a type advantage over the player's, while the other picks the one that has a type disadvantage over the player's. In the core series games (with two exceptions), the player can choose a fire, water, or grass-type starter Pokémon at level 5.