Caveman is the slang term for neanderthals. They are early humans who relied almost entirely on the wilderness around them for commodities. In Ook and Gluk: Kung Fu Cavemen from The Future they inhabit a small town called Caveland. A group of cavemen also appear in the 10th Captain Underpants book when George and Harold are teleported to the plains of Africa where they teach them English through drawing and eventually, inventing the world's first comic. They then retaliate against Tippy Tinkletrousers and eventually are saved after Captain Underpants makes them warm up inside the fabric of Tippy's robot trousers.