If we were meant to fly, we'd have propellers on our heads and jet engines on our backs.
Grandpa SquarePants is the father of Harold, Sherm, and Blue. He is also the paternal grandfather of SpongeBob, Todd, BlackJack, and Stanley. He is voiced by Tom Kenny. He very much resembles SpongeBob's square shape.
He is first mentioned in "
Rock Bottom," and is depicted in SpongeBob's mind in " The Sponge Who Could Fly." He is known for his wise sayings, which include "If we were meant to fly, we had have propellers on our heads or jet engines on our backs." (" The Sponge Who Could Fly") and "Never run for a bus, especially one that's going up at a 90 degree angle." (" Rock Bottom").
He was born to a Mr. and Mrs. SquarePants. Mrs. Squarepants might be
SpongeBob's Great Grandmother.
He married a female sponge who is now called "
Together, they may have bought the home that is now known as
Grandma SquarePants' House, but this has not been confirmed.
Harold, Sherm, Blue, and one other son and one daughter, one other son and two daughters, two other sons and one daughter, or three other sons.
He once said "Never run for a bus, especially one that's going up at a 90 degree angle."
and "If we were meant to fly, we had have propellers on our heads or jet engines on our backs." 
Late in his life, he had a cane
then eventually a walker. 
At some point, he died as his wife currently lives alone with there being no mention of him.