She wears a long dark pink dress and light green slippers. Her skin color is similar to Squidward's, only slightly darker. She has gold earrings and white hair. She also has red eyes.
In "Chum Fricassee," Grandma Tentacles was shown to be extremely abusive towards Squidward, such as frequently stomping on his foot with her walker and telling the customers to destroy the Chum Bucket. On the other hand, Squidward had cooked her recipe incorrectly, thus giving the customers severe stomach problems, so her anger was justified.
The octopus now known as "Grandma Tentacles" was born to unknown parents.
She married an unknown Mr. Tentacles.
She gave birth to Mr. Tentacles, the father of Squidward Tentacles.
Despite her rather antagonistic side shown in "Chum Fricassee," she was briefly mentioned by Squidward in the episode "The Two Faces of Squidward." Squidward said that she gave him homemade soap thus indicating that she did love and care for him at a certain point.
She looks very similar to Mrs. Tentacles, despite being her mother-in-law.
She must be extremely old as she has a grown grandson and a son way past that of middle age.