Someone told me that in Battle Revolution you can enter codes for some Pokemon your pearl game is this true and if so what are the how do I use them they unlock?

You are likely thinking of Pokémon Battle Revolution, which is a Wii game, not Pokémon Pearl, which is a Nintendo DS game.

It's not possible to use codes to directly unlock Pokémon from Pokémon Pearl into Pokémon Battle Revolution.

Here's why:

* Different games, different save data: Pokémon Pearl and Pokémon Battle Revolution are separate games with their own save files. You cannot transfer data directly between them.

* No in-game code functionality: Pokémon Battle Revolution does not have any in-game functionality to use codes to unlock Pokémon.

How to get Pokémon in Pokémon Battle Revolution:

1. Connect your DS to the Wii: You can connect your DS to the Wii using the Nintendo Wi-Fi Connection.

2. Transfer Pokémon using the "Pokémon Transfer" feature: This feature allows you to transfer Pokémon from your DS games (like Pearl) to Pokémon Battle Revolution.

3. Play online and receive Pokémon: You can participate in online battles and earn rewards, including Pokémon.

4. Participate in events: Nintendo often holds special events for Pokémon Battle Revolution, offering exclusive Pokémon.

Important Note: The Nintendo Wi-Fi Connection service is no longer active, so you will not be able to transfer Pokémon from your DS games to Pokémon Battle Revolution or participate in online events.

If you're looking to play with your Pearl Pokémon in a more recent game, you might consider transferring them to Pokémon Bank and then into a newer game like Pokémon Home, allowing you to access them on the Nintendo Switch.