Harold[2] SquarePants is SpongeBob's father and Margaret's husband. Unlike their son, who is a squared-off tube sea sponge, Harold and his wife are designed as round sea sponges. Although both SpongeBob and his parents are modeled after real-life species of sea sponges, their markedly different appearances have not been explained.

The decision to have SpongeBob's parents resemble round sea sponges was a reference to SpongeBob's original design.﻿[citation needed]