Bozo's circus sets up near the "Great Tar Pits." The noise wakes up a dinosaur in the tar pit who causes chaos until Bozo lures him back into the tar. The circus owner sets off explosions, which cause an earthquake. Bozo falls into an underground lake which leads to catacombs containing giant animals and people called the Tar Men. Bozo makes their King laugh and is given the giant animals. He is given two potions, one which will shrink the animals, another that will make them large again. His boss destroys the enlarging potion, but Bozo's circus is still a success with the miniature animals.