Dex and Kayla are trying to complete Dino Experiment 1024 "What is a T. rex like on the inside?" when Dad convinces them to go on a fantastical animated adventure inside a T. rex to see her massive stomach, heart, lungs, and not so massive brain.

When Dana visits, Dex convinces her and her friend Riley to play her old DIY board game "Game of Bones" with him and Kayla. But this time, instead of dinosaurs, the players must choose a prehistoric mammal to see who was built for survival.