Aunt Sponge (also simply known as Sponge) is one of the two main antagonists of the 1996 Disney film James and the Giant Peach (which is based on the 1961 children's novel of the same name by the late Roald Dahl), the other being Aunt Spiker. She is one of James' two cruel aunts and Aunt Spiker's sister.
After the death of James' parents, Sponge and Spiker had no choice but to take in James and "raise" him. Instead of caring for him, she and Spiker force him to do every work around the house, they had a tendency to beat him when he disagrees with them or backtalk, and almost always make him go into his room without dinner. She and Spiker make fun of poor James, and they never call James by his name, but always refer to him with mean, insulting, and opprobrious names such as "you nasty little beast".
Aunt Sponge is a greedy, selfish and morbidly fat woman, who is equally cruel, repulsive, unsympathetic and vituperative as her sister Spiker, and presumably the younger of the two. Both she and Spiker are vain, each singing praises of their imagined beauty while they are actually grotesque, but each usually ends up attacking the other's repulsion. Dominated by Spiker, Sponge is apparently a bit more dimwitted, gluttonous, and acquisitive, thinking of eating the peach while Spiker seizes the money-making and remunerative opportunities it will bring to make them rich. According to the musical, Sponge also has "voluptuous curves" and a "solid gold tooth". Sponge attempts to save her own life instead of Spiker's when she notices the giant peach rolling towards her. However, they trip up over each other and both meet the same end.
Sponge and Spiker adopted James after his parents were eaten by a rhinoceros and are very abusive and treat him like a slave, forcing him to do hard labor and feeding him nothing but fish heads. Both have a terrible hatred of insects and bugs and kill them in a variety of awful ways, and are thus hated by them as well. It is unknown if Spiker and Sponge are the sisters of James' father or mother. In the book, the illustrations show them to be elderly, so they could also be his great-aunts.
Sometime later, she and Spiker discover a peach on a withered old tree, and watch it grow to immense proportions in a matter of seconds. She and Spiker use the giant peach as an attraction, making lots of money as James watches from the house, not allowed to leave or play with the other children. That night, she and Spiker send James outside to pick up the garbage dropped by their customers.
Later, when James escapes on the giant peach, he is followed by her and Spiker all the way to New York, apparently somehow managing to drive their now-crushed car under the ocean and reach New York covered in seaweed and crabs, where they try to convince the authorities that James is a liar and that he be released to them. One night, while navigating on the peach, James has a nightmare of him as a caterpillar being chased and attacked by Spiker, Sponge, and the rhino, eventually getting trapped in a blind alley before he awakens. However, James, now no longer afraid of her and Spiker, stands up to them and reveals the truth about their horrible treatment of him.
Disbelieving that James dares to stand up to them, she and Spiker furiously attack him with firemen's axes until the sudden reappearance of the insects, who all come to James's rescue. James and the bugs tie her and Spiker up with Miss Spider's thread, and the beat cop has them taken away on a crane. What happens with Sponge and Spiker afterwards is completely unknown, but most likely, the two sisters were arrested for child abuse after being taken away, paying for their crimes once and for all. Another possibility, however, could be that, with their faces clogged with spiderweb, they were not able to breathe and suffocated to death, though it's plausible that James would have not allowed to let his aunts die even though they tried to kill him.
After the credits, there is a scene showing an arcade-like game which consists of controlling a rhinoceros to attack replica models of her and Spiker.
In the book, when the peach gets loose and rolls, it rolls over her and Spiker, killing them both, and they subsequently do not reappear at the end.
In the 1996 film, they survive and pursue James to New York City in their beat-up car (in the Ice World, James and Miss Spider see a shipwreck with figureheads, having a terrible resemblance of the two aunts). Upon arriving in New York, both are soaked as if they had been driving their car across the seabed. They attempt to kill James but are tied up with Miss Spider's silk and arrested.
In the 2015 musical, which combines material from both the book and the film, James' aunts survive like in the film. However, the peach lands atop the Empire State Building, and eventually it falls off at the story's climax. As such, Sponge and Spiker are both crushed to death by the peach-pit like in the book.
Spiker and Sponge in the book
Spiker and Sponge in the original 1961 book
Spiker and Sponge ordering James about
Spiker and Sponge in their lounging clothes
Spiker and Sponge posing for a picture
Spiker (right) and Sponge (left) after they chased James and the peach from England to New York
Spiker and Sponge in anger
Spiker and Sponge tied by Miss Spider's string after James exposes them of their true colors
Both the novel and the film never specify whether Sponge and Spiker were the sisters of James' dad or James' mom. However, considering that in the film they insulted James' dad, it is possible that they were sisters of James' mom at least in the film canon, though they also mocked about her, albeit not so bad like they did with his father. Another explanation could be, also, that they are actually James' great-aunts, especially considering that they are depicted to be old in the book.
Aunt Sponge was portrayed by Miriam Margoyles, who also voiced the Glowworm in the same film, and later voiced the Matchmaker in Disney's Mulan.
When James and Miss Spider were searching for both Mr. Centipede and a compass, one of the sunken ships had both the aunts on the mast for unknown reasons. Interestingly, both Miss Spider nor James take note of this and such matter even doesn't go adressed later on.
When the aunts arrive on New York, it is implied that they drove their car underwater, which is really irrealistic, considering the distance between England and New York and how they would have been able to not breath during all that time. A possible explanation could be that when the peach rolled over the car, it could have given magic powers to the vehicle and her occupants, and thus the car was given the ability to be drivable underwarter and the aunts were given the ability to breathe underwater or hold the breath for days.
The aunts has similarities to Lady Tremaine from Disney's Cinderella, as three of them force the protagonists of their respective films to work like slaves.