They are giant Arachnid like creatures. They carry cocoons on their backs which were mistaken to hold hostages when it only held potoatoes and crops the Unkbuut farmed.
They are caring, friendly, good-natured creatures. They are very intelligent almost to a human level degree, understanding human speech and that they were the cause of the earthquake, offering to help. They are also farmers and vegetarians.
The Unkbuut were burrowing underground Agrabah, not realizing the land was weak and brittle, creating an accidental earthquake/cave in as a result. Aladdin and his friends were helping people evacuate but Aladdin came across one of the Unkbuut and fainted. Later, the Unkbuut queen kidnaps Jasmine to show her they are actually peaceful. Aladdin and his friends go underground with Genie disguised as one to follow them only to discover Jasmine fine and telling them the Unkbuut are peaceful creatures. Meanwhile, Farouk leads a mob with torches to kill the Unkbuut but through their haste they accidentally burn a crater, with a child in the middle. The Unkbuut queen helps Aladdin rescue the boy and everyone realizes the Unkbuut are friendly. The Unkbuut then help repair the city, with the boy asking his mother to tell him a happy story of the Unkbuut.