There’s actually a way to select Pikachu as your starter in Pokemon GO. If you don’t want to start with Squirtle, Charmander or Bulbasaur, you can opt for the Pokemon mascot in reminiscent of Pokemon Yellow. To have Pikachu in Pokemon GO from the get-go, reject going with Squirtle, Charmander and Bulbasaur by physically walking away from them. They’ll reappear a few more times, but keep ignoring and walking away from them until the fifth time, when Pikachu will finally be displayed alongside them. After this, select Pikachu on the map to throw a Poké Ball to catch it. You may have to walk a bit more, but it’ll be worth it once you have this cutie by your side:
How to get Pikachu as your starter in Pokemon GO
Pokémon Blog 