The Jetsons Meet the Flintstones (1987) on Netflix

Plot summary

In the space age, Elroy Jetson works on a time machine while his father George faces trouble at work. Mr. Spacely's rival Cogswell has been taking company ideas, and Spacely suspects George of being on Cogswell's side. Spacely orders George to watch Cogswell and prove himself innocent. In the Stone Age, Wilma and Betty want a vacation in Honolurock, but Fred Flintstone dreams of the poker tournament at the Water Buffalo lodge. He and Barney Rubble skip their late shift, play against Mr. Slate in disguise, and are fired. Elroy finishes his machine, and the Jetsons set out on a trip that brings them to the Stone Age, where Fred and George meet and the two families become friends.