How do you get the fast ball in Pokemon pearl?

You can't get the Fast Ball in Pokemon Pearl! It's a generation 5 Poké Ball, introduced in Pokemon Black and White.

The Fast Ball is designed to increase the chance of catching Pokémon that are faster than the player's Pokémon. It's an excellent choice for catching Pokémon like Ninjask, Garchomp, or other fast creatures.

Unfortunately, Pokemon Pearl is from generation 4. There are plenty of other Poké Balls in the game to help you catch Pokémon, like the Poké Ball, Great Ball, Ultra Ball, and Master Ball. Each has its own capture rate and might be more useful for certain Pokémon than others.

So, if you're playing Pokemon Pearl, you'll have to use those other options!