Billy Jim Plankton is one of Plankton's cousins. He is a hillbilly like the rest of Plankton's Cousins. He only appears in the episode "Plankton's Army."


He is an aquamarine plankton. He has three antennae that connect to a flap on his back that are darker than the rest of him. He has one eye, and is seen playing a violin.


He comes to the Chum Bucket after receiving one of Sheldon's numerous callings for the family's assistance. Once he enters the Chum Bucket, he is granted root beer if he and the rest of the family helped Sheldon steal the Krabby Patty secret formula. He later assisted him only to find out that the "secret ingredient" was mashed plankton.