The Adventures of Ook and Gluk

The book begins with a scientific disclaimer by professor Gaylord M. Sneedly, saying that the book "contains many scientific errors and stuff." He stated that dinosaurs and cavemen did not live at the same time, as dinosaurs lived 64 million years before cavemen. He then stated that he should know about it, since he was a recipient of "The Most Brilliantest Science Guy of the Whole Wide World Award" in 2003, a reference to the seventh Captain Underpants book.

However, George and Harold refute this via a "scientific disclaimer disclaimer". They said that scientists make theories based on evidence they discovered, and that everyday, all kinds of evidence are being discovered. They also mentioned that they have a time machine, and been time traveling to the future and past, discovering much evidence that scientists had no knowledge of, including dinosaurs and cavemen living at the same time. George and Harold stated that "scientists won't discover that until 2073." So they made "the world's first book based on science facts".

• Ook Schadowski – a Caveman who is best friends with Gluk. He later marries Lan, but is (twice) in the book losing his tooth.
• Gluk Jones – a Caveman who is the best friend of Ook, he later on married Ook's sister Gak, he has had an afro ever since birth.
• Gak Schadowski – Ook's sister who later becomes Gluk's wife.
• Master Derrick Wong – Ook and Gluk's kung-fu teacher from the 23rd century, who taught the two heroes kung-fu for many years. He is the father of Lan. It is unknown about his wife, so it is assumed he is either a widower or is divorced.
• Lan Wong – Master Wong's daughter, who later becomes Ook's wife and moves to Caveland to have her marriage, leaving her father.
• Mog-Mog – a tyrannosaurus rex who hated Ook and Gluk when they were kids, but became friends after Ook and Gluk saved her life.
• Lily Mog – Mog-Mog's dinosaur daughter. Lan named her Lily after her favorite flower, she always vomited when doing kung-fu. After she was far away from Mog-Mog after Chief Goppernopper's destruction, Ook and Gluk had to look after Lily.
• Big Chief Goppernopper – The dictator of Caveland and one of the two antagonists.
• J.P. Goppernopper – The Chief Executive Officer of Goppernopper Enterprises and the descendant of Chief Goppernopper. He is one of the two antagonists.
• Gluk Jones Jr. – The son of Gluk and Gak Jones.
• Ook Schadowski Jr. – The son of Ook and Lan Schadowski.
• George Beard – Author of Captain Underpants. (Only appeared in the About the Author and Illustrator page).
• Harold Hutchins – Illustrator of Captain Underpants, Super Diaper Baby, The Amazing Cow Lady and Hairy Potty. (Only appeared in the About the Author and Illustrator page).
• Professor Gaylord Sneedly - The scientist and father of Melvin Sneedly, George and Harold's nemesis.

The book was at #2 on the New York Times hardcover graphic novel best-sellers list its first week of release,[2] and remained at first place for six consecutive weeks. It served 33 weeks on the list,[3] its period on the list overlapping with the paperback edition's presence on the paperback best sellers list.[3]

School Library Journal described the book's humor as "completely immature, and for the target audience, completely hilarious". Booklist suggested that the book would "appeal to those who like silly adventures, puke-based humor, and kung-fu fighting."