Fred Flintstone and George Jetson both have back-breaking jobs and families to support, but they find out more about each other the day that George's son Elroy builds a time machine and the family thinks its a joke but decides to try it out anyway. It was built to take them farther into the future, but instead--thanks to Astro--they get sent back to Prehistorica Days; back to the town of Bedrock. On vacation, Fred and Wilma Flintstone and Barney and Betty Rubble meet the Jetsons and think they're beings from another universe. Fred passes George off as his cousin, and all goes well until the time machine accidentally transports the Flintstones into the future, so while the Flintstones and Rubbles adjust to a space-age, robotic, automatic life, the Jetsons must adjust to a rocky, stony, pedal car, no-shoe, no-picture-phone, no-Mr.-Spacely Stone-Age life. Meanwhile, Henry Orbit and Rosie have built a new time machine and Rosie goes off to find the Jetsons, meeting Robin Hood and many other famous faces along the way. Will the Jetsons ever see their space city again? Will the Flintstones ever see Bedrock again? Will Fred keep his job with Mr. Spacely? Will Barney keep his job with Mr. Cogswell?