Illustrations and rhyming text reveal the Underpants War as the reason dinosaurs became extinct.

Oona finds a giant egg and brings it back to West Woggle to care for it, and see what hatches--but others in the cave want to claim her egg, particularly the nasty kid Bruce Brute, and when the baby stegosaurus hatches it will have to choose who it wants to live with.

Pablo and Tyrone must get past Greek Gods Austin and Uniqua on a samba-filled journey up Mt. Olympus to convince Weather Goddess Tasha to stop raining on their Sports Day. Then, it's an out-of-this-world adventure as aliens Zablo and Zuniqua become Rancher Tasha's ranch hands to earn the pancakes they need to fuel their ship. Next, Tyrone is the best dolphin racer in Atlantis, but Stable Girl Uniqua hopes to beat him with her wild dolphin Sea Squirt....

With school out Oona and her brother Bonk are busy helping their father gather food, but Oona's pet Stegosaurus is something of a cave wrecker when left at home all day, so the children start Camp Woggle where all the local pets can amuse themselves during the day--but Mauro's pet T-Rex is a problem because he has a tendency want to eat the other campers.