<Tr> <Th> Pets </Th> <Td> Spot (pet amoeba) </Td> </Tr> <P> Sheldon James Plankton and Karen Plankton are fictional characters in the American animated television series SpongeBob SquarePants . They are respectively voiced by Mr. Lawrence and Jill Talley . Their first appearance was in the episode "Plankton!" that premiered on July 31, 1999 . They were created and designed by marine biologist and animator Stephen Hillenburg, the creator of the program, with additional character development by Lawrence . </P> <P> Plankton is an intellectual planktonic copepod who runs the unsuccessful Chum Bucket restaurant alongside Karen, who is a talking supercomputer . Plankton is the arch - rival of Mr. Krabs, who owns the far more profitable Krusty Krab restaurant and sells a fictional burger called the Krabby Patty . Plankton and Karen often devise schemes to steal the secret Krabby Patty recipe, but their efforts are always thwarted by Krabs and his employees . </P> <P> Critical reception for Plankton and Karen has been positive, with praise directed toward their voices and dialogue together . They began as minor characters, but Lawrence developed their personalities throughout the show's early seasons and they eventually became the franchise's main antagonists . The Planktons play central roles in the 2004 theatrical film, which promoted them both to main cast members in its credits, and the 2015 sequel . They have also been featured in a variety of spin - off media, including tie - in publications, playsets and other merchandise . </P>

What type of animal is plankton from spongebob