Is having Pikachu over Pokemon Trainer in the first Smash Bros prioritizing Pikachu spinoff games?
Pokemon was always an odd case though, Pokemon are the one who fight in Pokemon, and Pikachu is playable in every single mainline Pokemon game. Smash even references the trainer battles since the first game by showing the coming out of Pokeball animation like in the in-game battles. Even when Pokemon Trainer was added, the entire gimmick is just that he allows real time switching between three different Pokemon during a battle, rather than fighting directly.