King Cobra is the alias of one of Billy and Mandy's fellow elementary school students, a large boy with blond hair. In the school, 'King Cobra' has the social status of a nerd.
In his debut episode, 'King Cobra' is a member of the Secret Snake Club; in the Secret Snake Club, 'King Cobra' is really just his codename. Along with his fellow 'snake nerds'--'Wiggly' and 'Viper'--'King Cobra' seeks the destruction of all the cool kids in the school, as the none of them are cool. To achieve this, they seek to summon "Shnissugah", a supposed patron and protector of Nerds just like themselves. His singing voice sounds an awful lot like Bob Dylan's singing voice.