What was Pokémon Yellow’s official subtitle in English?

Pokémon Yellow’s official English subtitle was Special Pikachu Edition.

The full English title was Pokémon Yellow Version: Special Pikachu Edition. It was an enhanced version of the first-generation games, designed to resemble the Pokémon anime more closely than Pokémon Red and Blue.

Pikachu followed the player outside its Poké Ball, and the opening choice structure was changed so players received Pikachu rather than selecting Bulbasaur, Charmander, or Squirtle. Jessie and James of Team Rocket also appeared in the game.

The title is frequently shortened to Pokémon Yellow, which is perfectly understandable in ordinary conversation. However, “Special Pikachu Edition” is the official subtitle and distinguishes the game from informal names such as “Pikachu Version.”