Instructions
Purchase Pokemon Ruby, Sapphire or Emerald. One of these three games are needed to receive a Mudkip. In the main menu of the game, select "Start New Game." When required, enter your Pokemon trainer's name and select his gender. Click "A" to progress through the dialogue, and begin game play.
Exit the house when the game begins. Talk to the people in Littleroot town to receive information on Professor Birch. He is under attack by a wild Pokemon named "Poochyena." Travel upwards until you reach the town exit, where Professor Birch is currently under attack.
Approach Professor Birch to initiate a Pokemon battle. Birch will ask you to select a Pokemon from his bag to do battle with the wild Poochyena. Select the "Mudkip" from the bag, and use it in your battle with Poochyena.
Attack the wild Poochyena with the "Tackle" attack. Repeatedly hit the Poochyena until he loses all of his Health Power (HP) and faints. Professor Birth will be grateful you saved his life and give the trainer the Mudkip as a reward.