Unfortunately, there is no Action Replay cheat code that makes Pokemon always want to join your team in Pokemon Mystery Dungeon: Explorers of Darkness.
The Action Replay modifies game data, but recruitment depends on dynamic in-game factors:
While you could theoretically modify these factors with advanced technical knowledge, it's not a simple cheat code. Using Action Replay also risks game crashes or data corruption.
Better Approach: Focus on increasing friendship and understanding recruitment mechanics for a more rewarding experience.