Heterosexuality
So you claim to liek Mudkips? Well then, you are an unholy anime fag with a penchant for that fag-out-of-Pokemon's dick. But that is fine, really—to each his own.
Spawned from a DeviantArt comment inviting someone to their Pokémon group, the comment basically used the person's apparent like of Mudkips to perhaps entice the user to join their group. Whether or not said person actually joined is unknown.
It eventually spawned a very popular piece of copypasta on 4chan's /b/ telling a story about someone at a school asking "So i herd u liek mudkips" to some retard who screams back "I LUUUUUUUUUVE MUDKIPS!" This resulted in the retard dry humping a Mudkips doll in the school hallways.
Since then, many people have become obsessed with Mudkips.