Discussion WesternAnimation / TheJetsonsMeetTheFlintstones

Moving all of this here because it is excessive and spoileriffic.

Synopsis taken from The Other Wiki:

While Elroy is busy working on a time machine (with Henry Orbit's help), George is ordered to come to Mr. Spacely's office for a discussion. Cogswell has been stealing Mr. Spacely's business ideas under his nose; blaming George for the problem, Mr. Spacely orders George to go spy on Cogswell. Disguised as Cogswell's robot dog, Centro, George finds out that Cogswell's new robot computer, S.A.R.A., has been seducing the Spacely robot computer, R.U.D.I., into leaking Spacely's secrets to her. Upon finding this out, George tries to go tell Mr. Spacely, but R.U.D.I. won't let him.

Thousands of years in the past, Wilma and Betty are trying to butter up Fred so that he'll agree to have their vacation in Honolurock. Fred, wise to their plan, ignores their advances and, while at the quarry, tells Barney that he plans to take the girls some place even better with the winnings he believes he will make at a poker game at the Water Buffalo Lodge tonight. Mr. Slate, however, wants him and Barney to work a late shift (Mr. Slate is in danger of losing his company to Turk Tarpit, the owner of Tarpit Productions, a rival company), but they go to the poker game anyway, believing that Mr. Slate will never find out. But Mr. Slate is also at the poker game, so Fred tries disguising himself as a rich Texan (and Barney as his ladyfriend). Unfortunately, thanks to a spider intervening on the game, not only does Fred lose to Mr. Slate, but he and Barney are soon exposed, and Mr. Slate fires them.

Back in the future, Elroy finishes up his time machine. George doesn't believe it really works until Elroy uses it to send a girl he brought from Arabian times back to her own time. The Jetsons decide to use it to take a trip to the 25th century, with George wanting to get away from Mr. Spacely (and Judy wanting to get her mind off of a rock star boyfriend she just broke up with after seeing him with groupies). Right before Elroy gets the machine working, Astro accidentally sets the switch to "Past".

With no job, the Flintstones and Rubbles are forced to settle for a camping trip in the middle of nowhere (although Fred and Barney have not told their wives about getting fired), and without food as Dino has stowed away and eaten all the food they packed. Just as Fred and Barney are trying to set the tent up, the Jetsons show up in the time machine. At first, both sets of characters mistake the other for aliens until Fred and George eventually call out offering for peace. The families become fast friends (and Astro forms a friendly rivalry with Dino), and Fred, amazed by George's expand-o-matic bag containing futuristic gadgets (such as the anti-gravity belt and boots), decides to use the Jetsons' things to help Mr. Slate win against Turk Tarpit at the company picnic the coming week.

At the picnic, while Judy falls for a rock star named Iggy Sandstone, Fred introduces George to Mr. Slate, claiming him to be his distant cousin. Mr. Slate is reluctant at first to trust George, but since he is two points behind Tarpit, he accepts that he needs some help, especially with Tarpit's obvious cheating and the commentators constantly ridiculing him for "losing as usual", in exchange for giving Fred and Barney their jobs back with several advantages. When Tarpit cheats in the next event, which consists of throwing dinosaur shoes at a pole (which is actually the neck of a turtle-dinosaur instructed to accept only those thrown by Tarpit and deliberately miss Mr. Slate's), George uses his magnetic boots to make Mr. Slate's shoes land on the neck and Tarpit's miss, thus making Mr. Slate the winner by default. The next event is a footrace over a vat of hot coal (Tarpit again tries to cheat by putting thick socks on), and Fred enters for Mr. Slate, wearing George's anti-gravity belt. Despite falling over and burning his bottom, Fred manages to beat Tarpit and even Mr. Slate's score against Tarpit. Unfortunately, during the last event, which consists of catching a "pigosaurus" in the mud, Astro and Dino's continued chase scares the pigosaurus enough for it to jump in to Tarpit's hands, making Tarpit the winner of the picnic. Enraged, Mr. Slate goes back on the deal and fires Fred and Barney again.

While Mr. Spacely continues to vent over his failing business, Henry and Rosie assemble a time machine retriever in order to bring the Jetsons back home. But just when they get it to work, the time machine does indeed return - but, due to a mishap, it ends up bringing the Flintstones and the Rubbles instead of the Jetsons. At first, Henry, Rosie, and Mac mistake the newcomers for the Jetsons, and so does Mr. Spacely. Upon seeing that they really are cavemen, Mr. Spacely introduces them to the press.

Stuck in the past, George asks Mr. Slate for a job. Slate, still angry at George for the picnic accident refuses at first, but when Tarpit offers to make George famous himself, Slate immediately employs George, making him his partner. As a "flying man from out of this world" (thanks to his anti-gravity belt), George becomes famous, and this makes the family so rich that they buy ownership of several local Bedrock-area businesses, including George buying a whole car lot and half of downtown Bedrock, Jane possessing a clothing store and several beauty salons, and Judy becoming the manager for Iggy's band. Pretty soon, though, the Jetsons begin to experience great stress with their businesses. George cannot deal with the stress of owning so many businesses, Jane is not prepared for the pressure of owning so many clothing stores, and beauty salons, and to make matters worse, Judy goes through déjà vu when Iggy also leaves her for some groupies.

Mr. Spacely makes Fred the spokesman for his company, but R.U.D.I. accidentally leaks this information to S.A.R.A. Just as Mr. Spacely is introducing Fred to some important investors, Cogswell shows up and introduces Barney, who was jealous of Fred for taking all of the glory, as his news spokesman, coaxing the businesspeople to him. Spacely is furious, and Fred becomes angry with Barney to the point where he actually throws Barney out of the window (defenestration), although Barney survives the fall, and comes back asking him to throw him closer to the ground next time (the irony being that in the world of the Jetsons, there is no ground).

Meanwhile, Rosie asks R.U.D.I. to help her and Henry try to fix up the time machine so that they can go find the Jetsons. S.A.R.A. shows up at this moment and demands R.U.D.I. to get rid of Rosie; upon Rosie walking out, R.U.D.I. agrees that he'll do whatever he can to get the Jetsons back. They eventually do get it to work (it was just in the "off" position), and, after mistakenly landing in the Middle Ages, Rosie arrives in the Stone Age and finds her family. Able to return home, the Jetsons do so (taking Fred's car and Dino with them), but not before Judy reconciles with Iggy and tells him goodbye.

When Spacely sees Fred's ancient automobile, he decides to produce space-cars with an identical appearance. Cogswell tries to steal this information by sending Centro to take pictures (S.A.R.A. can no longer provide him information since R.U.D.I. told her off), but Dino and Astro manage to stop the robot dog from escaping, and Fred and Barney become friends again (Fred slipped off the rafter while chasing Centro and Barney saved him). Spacely's new retro-style space-cars become an overnight smash (Spacely even sells one to an anxious Cogswell provided he doesn't copy it). Judy is still feeling sad about Iggy, until she meets his descendant.

George turns his partnership with Mr. Slate to Fred, giving him and Barney their jobs back. However, Elroy tells them that the time machine has taken such a beating that it's broken for good now. All ends well, though, because when Mr. Spacely gives the cavemen their original automobile back, they're able to return to the Stone Age due to having absorbed the time machine's quadrapotents (or as George puts it, "that old car wants to go home as much as they do!"). George and the others wave farewell as Fred, Wilma, Barney, Betty, and Dino vanish. The film ends with Fred screaming out his most famous catchphrase "Yabba Dabba Doo!"