Earl decides it's time to potty train Baby so he can avoid changing anymore diapers. But the idea doesn't go over well with Baby and he runs away into the wilderness.
Earl's new job involves picking hit shows for television; but the show he puts on the air make their viewers unbelievably stupid and he must find a way to make everybody smart again to save society.
The search for a missing golf ball leads Earl into a new world that he proclaims as his own territory; but Robbie suspects that the land really belongs to the cavemen who inhabit it.
After the Baby pulls a stunt that scares Robbie half to death, he decides to tell the Baby a true, terrifying story: He has been bitten by a bloodthirsty creature known as a wereman and will become one when the moon is full.
The Baby gets sick and Fran demands Earl take them to the doctor. Modern medicine only makes the Baby sicker; leaving Fran and Earl to ponder an alternative healer and Ethel knows the perfect dinosaur for the job: A guy in the woods.
Robbie falls in love with a new girl, Wendy, who happens to be Richfield's daughter. Richfield takes well to Robbie dating his daughter, but Robbie is warned that Wendy's involved in a dangerous secret involving her previous boyfriends.
When Earl loses his temper at the baby, he also loses his parenting license. When he flunks the test to get it back, the parenting police move in the house and monitor how Fran parents the kids by herself.
When told to come up with an original idea for school, Charlene hits upon the notion that the world is round. However her discovery lands her in jail which begs the question how free dinosaurs are to think and say what they believe.
Earl and his friends drag Robbie and the Baby off for a camping trip while Fran and her girlfriends stay at home to visit but the gender roles become reversed when the females drink beer and the men get in touch with their softer sides.
Robbie gets fed up with Earl always telling him what to do, so he challenges Earl for male domination and wins but he quickly becomes aware of how much responsibility is involved in being the male of the house.
Charlene signs up for a foreign student exchange program to get away from her family who doesn't understand her; and the Sinclairs get a bitter taste of a different culture when a French bird moves in with them in Charlene's place.
The Chief Elder passes a law that forbids four-legged dinosaurs from living in Pangea. He demands they either marry a two-legged dinosaur or leave the country. Monica is threatened with deportation until Roy proposes so she can stay.
Baby becomes a hit sensation when he and Earl star in a series of commercials for a new frying pan. Earl is fired from the commercials and he and Monica start to worry that fame is going to the Baby's and Fran's heads.
Robbie tries to bulk up to impress a girl, but her attention seems to be drawn to a bigger guy named Dolf. When exercise doesn't cut it for Robbie, he resorts to Thornoids and finds out his new, bulky body comes at a high price.
Fran finds being a housewife and mother not fulfilling anymore and does volunteer work at a halfway house for amphibians. Earl gets stuck taking on the household chores and the kids and finds out what it's like being the mother.
Robbie is introduced to the wailing, funky blues sounds of "swamp music" and tries to bridge the species gap by getting a dinosaur record company to put out a mammal swamp music album.
Robbie starts doing the mating dance. Fran decides that the school needs to offer a course to the teenagers so they'll understand all about the mating dance, and Robbie is mortified when Fran is volunteered to teach it.
Ethel reads the Baby a story called "If You Were a Tree" about a dinosaur tree pusher who gets struck by lightning and swaps souls with the tree he's trying to demolish.
Robbie tries to get Earl interested in preserving Pangea. When Earl and Roy are ordered to bury toxic waste, they get a visit from an extraterrestrial from the planet Kyron who warns them to change their ways or face annihilation.
Charlene feels her family is neglecting her, so she gets their attention by winning the school talent show but her rising fame is riding on the backs of three young cavelings she found in the forest whose mother is looking for them.
