Grandma Plankton is Plankton's paternal grandmother and Plankton's father's mother. She was first mentioned in the episode Krabs vs. Plankton. She was called Gram-Gram in that episode. Her only physical appearance was in Gramma's Secret Recipe. She is voiced by Laraine Newman.
She looks similar to Plankton, except that she has glasses, dentures, puffy hair, and wears an orange dress that has green polka dots