She is a dark orange sponge who wears a light green and pink dress and light blue glasses and has light purple hair and pink lips. She enjoys making gingerbread men, chocolate chip cookies, and homemade sweaters with metaphorical love in every stitch. She also is very affectionate and likes to give a lot of kisses, as seen in "Grandma's Kisses."
She is shown to be a very kind and sweet grandmother to SpongeBob. She once treated him like a baby but later learns that he wanted to be treated like an adult, so she then started treating him as such and let Patrick take SpongeBob's place as a baby, though SpongeBob becomes jealous and wants his grandmother's affection back, so Grandma tells him that he doesn't have to grow up and can be treated like a baby as long as he wants.
In the comic Great Grandma, she is shown to have refined cultural tastes. She owns a stradiclarius and owns rare vintage clarinet records; she knows how to make a coral quiche with seaweed butter; she's a talented fine artist and modern dancer. In other words, she and Squidward have a lot in common, only she's much nicer and more welcoming.