|“||If we were meant to fly, we'd have propellers on our heads and jet engines on our backs.||”|
— Grandpa SquarePants, "The Sponge Who Could Fly"
Grandpa SquarePants is the father of Harold, Sherm, and Blue SquarePants. He is also the paternal grandfather of SpongeBob SquarePants, Todd, BlackJack, and Stanley, the husband of Grandma SquarePants, and the father-in-law of Margaret SquarePants (née BubbleBottom).
He is a pale yellow sea sponge with olive green holes and white hair. He wears a pine green shirt, a white undershirt, transparent light blue glasses, brown socks, and dark blue slippers. He also holds a black walking cane and a walker. Being an elder, his skin is rather wrinkled, and he appears to only have one tooth, which is on the right side of his mouth.
He is first mentioned in "Rock Bottom," where his likeness is exhibited through SpongeBob.
In his next appearance, he is depicted in SpongeBob's mind in "The Sponge Who Could Fly."
He was born to a Mr. and Mrs. SquarePants.
He married a female sponge who is now called "Grandma SquarePants."
He once said, "Don’t run for a bus, especially one that's going up at a 90-degree angle." and SpongeBob realized he was right when he tried running for a bus going up a 90-degree angle and "If we were meant to fly, we had have propellers on our heads or jet engines on our backs." which SpongeBob remembered when he was trying to fly.
- Out of the five times SpongeBob is seen old, he looks most like his Grandpa in "The Great Patty Caper."
- He has never appeared outside of thought bubble form, meaning it is unknown if he is deceased or probably somewhere away from Bikini Bottom.