To be honest, I don't give a sh*t about Pokémon Yellow. Its' a fan-service game based on the stupid anime. I said the
original Pokemon games, the ones that were first released. Yellow is not one of the original Pokemon games. If the anime was never made, then Yellow would have never been made. Now in Japan, the first two Pokemon games were Red & Green. The original third Pokemon game was Blue. Pokemon Yellow in Japan is regarded as an extra-fourth game (something that will never happen again), and when the games were being localized, they decided to use the Japanese Blue version to provide the engine (which is why the graphics in the US Red & Blue are different than the Japanese Red & Green), but essentially they are the same. For some reason they renamed Green version to Blue version, and decided to use Yellow as the third game.
If the anime was never made, there would have never been a Yellow version to start with, since Japan already had 3 versions. Obviously, in the Japanese Blue version, you don't start out with Pikachu, you have a choice of Bulbasaur, Charmander, or Squirtle. Blue version in Japan is just like Crystal, Emerald, and Platinum, an upgrade of the original paired versions. Notice how in Crystal, Emerald, and Platinum, the playable character doesn't look like Ash, and you
don't start out with a Pikachu, the starters are the same as the paired versions.
You see, I hate the anime, and I hate how some people think that Red and Ash are the same people.
Again, take a look at this picture:
https://bulbapedia.bulbagarden.net/wiki/Pokémon_Red_and_Green_beta#Female_player_character
Notice how Red has a Bulbasaur, not a Pikachu. Green actually has a starter, unlike his team in HG/SS. That was concept art for the original Pokemon games (which was drawn WAY before the anime was even thought of), and obviously, if they intended for Red to always have Pikachu, they would have made you start out with Pikachu in Red & Green, but they chose not to simply because they didn't want to do that.