Here's why:
* Poké Balls don't work that way: In Pokémon games, Poké Balls are used to catch Pokémon, not to make them appear.
* Slots are for gambling: The slot machines in Pokémon Pearl are used for gambling, not for catching or summoning Pokémon.
To get a Clefairy in Pokémon Pearl, you need to:
1. Find it in the wild: Clefairy is a Fairy-type Pokémon that can be found in the Grand Underground, specifically in the "Dazzling Cave" and "Glittering Cave" areas.
2. Breed it: You can breed a Clefairy with another Pokémon that can learn "Sweet Scent" to increase your chances of encountering one.
3. Trade for one: You can trade with other players to obtain a Clefairy.
Remember, there's no way to make a Clefairy appear from a Poké Ball on slots in Pokémon Pearl.