It is late Spring when Wally, Jeremy, Shades and Mario are at the La Brea Tar Pits working on a school research project and discover a mysterious tar egg that cracks open to reveal a friendly dinosaur.
Denver follows Jeremy to his job at the supermarket, where he hides in the storeroom and stuffs himself full of potato chips.
Wally borrows his sister Heather's video camera and the starry-eyed kids set out to make a video starring themselves.
While camping at a mountain lake with the boys, Denver is mistaken for a horrible lake monster.
Denver and the kids make friends with a circus owner's son and help him liven up a lackluster show with bicycle and skateboard stunts.
The boys decide to do a science project on dinosaurs for the school science fair.
Wally and Heather panic when they hear their parents are planning an out- of-town move.
Wally's first day on the job at the zoo takes a turn for the worse when the self-serving Dr. Funt captures Denver for his new high-tech exhibit.
The kind-hearted Denver rescues one of the boy's arch rivals, Scott, winning his heart and killing his plans to expose Denver to the media in order to gain publicity and votes for the upcoming student election.
While visiting Jeremy's Uncle Eli on his Nevada ranch, Denver and the boys attend a local rodeo.
Casey's movie-star cousin, Lana Lake, invites Casey, the boys and Denver to watch the filming of her latest sci-fi movie, "Leapin' Lizards on the Loose".
When Heather gets a job at a Dinosaur theme amusement park, Denver roams freely around the park and fits right in with all the dino-costumed employees.
Denver and Jeremy enter a wacky game show only to find they're competing against the team Morton Fizzback and Professor Funt.
Shades develops a recent interest in karate. He is also very into Nikko, the daughter of his instructor.
Denver becomes a major radio star during a competition between KAY-HIP and KAY-LOUD radio stations.
When Heather and Wally's parents inform the two that they are expecting guests from out-of-town, they must hide Denver that the local movie theater, which is believed to be haunted.
A boy genius, Freddy Facknitts, invents a time machine that sends Denver and Morton Fizzback into the past and into the middle of a crazy caveman competition called Mammothball.
When the boys enter Wally's dog, Rocky, in a relay race for dogs, they also disguise Denver as a dog so that Rocky will perform well.
Denver and Mario take a job as children's entertainers only to incur the wrath of Douggie, the Dancing Clown, who tries to sabotage Denver and Mario's entertaining efforts.
On a visit to Aunt Shadie's ghost town, the kids and Denver go on a wild mining car ride while trying to retrieve the deed to the town from some thieves who had stolen it.
Denver falls in love with a mechanical dinosaur and follows her into the Big Deal Movie Studios. His friends must get him home without being discovered.
When disreputable treasure hunters kidnap a valuable dolphin from a marine research facility and use him to locate sunken treasure, Denver dives in to save the dolphin.
Heather and the boys take Denver to a mountain ski resort.
The secluded beach where Mario surfs and the kids play is taken over by Rad Tad and his group of Surf Dudes.
