Plankton's Cousins first appeared in the episode Plankton's Army. They appear and act in the manner of a modern hillbilly. The majority of them can read except for one, Clem. Unlike Plankton, they're not evil. They wanted rewards if they helped Plankton, such as memory for their laptops, an extra string for a banjo, matching boots, but all of them wanted root beer. Some of his cousins appeared in One Coarse Meal.
Because they all were hillbillies, it would be obvious that little things could please them.
One common like between all of them is their enjoyment of root beer. They are also fond of Plankton's computer wife, Karen. They also laugh quite a bit, when Karen was joking about Plankton's first name (Sheldon).