Here's how it works:
1. Talk to the old man in the Viridian City Poké Center: He will tell you about a special Pokémon hidden somewhere in the Kanto region.
2. Go to the Safari Zone: This is the only place where Shiny Mew can be found.
3. Explore the Safari Zone: Keep searching the grass until you encounter a Shiny Mew. It can be tricky to find as it has a very low encounter rate.
Important Notes:
* You need to have already caught all 150 Pokémon in the game.
* You need to have the National Pokédex.
* This event is only available after defeating the Elite Four six times.
* Once you catch Shiny Mew, you can't encounter it again.
So, beating the Elite Four six times is a challenging but rewarding feat that lets you catch one of the rarest Pokémon in the game!