Mudkip is exclusive to Pokémon Ruby, Sapphire, and Emerald.
Here are some ways to get a Mudkip in Pearl:
* Trading: The most common way is to trade with someone who owns a Pokémon Ruby, Sapphire, or Emerald. You could find someone online or in person who is willing to trade.
* Event Distribution: Occasionally, Nintendo will distribute special Pokémon events that include Mudkip. However, these events are typically limited-time and may not always be available.
It's important to note that if you have a copy of Pokémon Diamond, you can also catch a Mudkip by trading with someone who has a copy of Pokémon Pearl. However, you'll need to trade a Pokémon that is exclusive to Diamond to get a Mudkip in return.