If you have ever downloaded a popular ROM hack like Pokémon Rocket Edition and tried to play it, you likely encountered a ReadMe file that said:
Some of the highest-rated Pokémon experiences in existence would not work without this specific ROM base: firered 1636
In the future, as hackers move toward the Nintendo DS era (using HeartGold or Black as bases), the "1636" era may eventually fade. However, for the last two decades, this specific string of numbers has represented a gateway. It is the bridge between the official games we grew up with and the infinite creativity of the fan community. If you have ever downloaded a popular ROM
and expanded Pokédexes with up to 900+ Pokémon. Top Fan Games That Use the 1636 Base and expanded Pokédexes with up to 900+ Pokémon
This confuses new players constantly. Here is the explanation of that process: