Initially, Mudkip is a cowardly Pokémon that longs to become stronger and form a rescue team. He idolizes Alakazam of Team A.C.T..
History
After meeting Ginji and seeing his determination, they team up to form a rescue team. He accompanies Ginji on his adventures and remains extremely loyal to him.
Throughout the story, Mudkip becomes braver and stronger. One example is when he befriends Gengar despite the fact that Gengar had mistreated them before.
At the end of the story, when Ginji becomes a human again, it is revealed that Mudkip continues rescuing Pokémon.