Margaret SquarePants (née BubbleBottom) is Harold's wife, SpongeBob's mother, the daughter-in-law of Grandpa and Grandma SquarePants, sister-in-law of Captain Blue and Sherm, and the aunt of Larry, Todd, Blackjack, and Stanley. She has black hair and is dressed in a purple matchbox dress with matching sleeveless pantalets with purple high heels and has a pearl necklace. She resembles a sea sponge whereas SpongeBob more resembles a kitchen sponge.
She debuted in "Home Sweet Pineapple," where they came to pick up SpongeBob after nematodes ruined his pineapple house. In this episode, when SpongeBob is in his parents' car, he says: "Good-bye Bikini Bottom!" which indicates that SpongeBob's parents don't live in Bikini Bottom. They later appear in "Culture Shock" as they watch the Krusty Krab talent show, and in "No Free Rides," where they gave their son a boat mobile for passing his driver's test. In Driven to Tears, they seem sad that SpongeBob doesn't have his license, saying "Even Patrick has a license." Margaret is voiced by Sirena Irwin. It is revealed that her maiden name is BubbleBottom. It is also revealed in "A SquarePants Family Vacation" that her name is Margaret.
She was born as Margaret BubbleBottom to Mr. and Mrs. BubbleBottom.
She married Harold SquarePants and changed her name to Margaret SquarePants.
She had one child named SpongeBob SquarePants.
She once told SpongeBob to never run with a broom.
She always told SpongeBob not to look for trouble.
She now lives only with her husband since SpongeBob moved out.
Oddly, the Q&A section of the official SpongeBob SquarePants website for New Zealand states that her name is Claire Gretchen SquarePants.  This however is false.
In the credits, it lists her as Mom, and sometimes Mother SquarePants.
The hat she wears is either black or purple.
It is revealed in "Whelk Attack" that her maiden name is BubbleBottom.