From the Pokémon Encyclopedia
Mudkip is the water-type Pokémon starter in the Hoenn region in the games Pokémon Ruby, Sapphire, and Emerald.
In the anime,
Brock gets a Mudkip after winning the trust of
Old Man Swampy, who styles his hair like a Mudkip. In the events leading up to this, Old Man Swampy offers to let Brock see his eggs hatch. Brock agrees, and is treated to the sight of a baby Mudkip hatching.
Old Man Swampy suggests that Brock take one of his older Mudkips. At the last minute, Brock asks the Mudkip's permission, and it agrees and decides to join Brock for all the great adventures they will have together. However, within a couple of episodes it ends up spending almost all its time in Brock's Poké Ball.
Later, Brock's Mudkip evolves into a Marshtomp and eventually a Swampert.
Internet Fad
Mudkip is also a major fad on most gaming sites. it started when one 4Chan user said to another "so i heard you leik mudkipz?"[1] it is not known why the spelling was not fixed
Refrences
1 Bulbapedia artice on mudkip http://bulbapedia.bulbagarden.net/wiki/Mudkip_%28Pok%C3%A9mon%29#Trivia
