He is a very elderly crab, being between the ages of 120 or 160 years old, with light pink skin and the same clothes as his great-grandson Eugene. His right eye has a white pupil and he has to use a wheelchair to move around. Mr. Krabs refers to him as "Great Grandpappy Krabs."
He was born to a crab now known as Great Great Grandpa Krabs and an unknown Mrs. Krabs.
Role in episode
He is one of the various relatives who Mr. Krabs summons to fight against Old Man Jenkins and his family.
Great-Grandpa is shown to be very senile and is confused as to where he is, and Mr. Krabs tries to get him to make his annoying customer leave, but it does not work since Jenkins brings out his great grandfather, who is older.