@angrybrony
I’ve seen those too.
But also I have seen one that says that The Flintstones is a the post-apocalyptic future but The Jetsons is far after it, basically being a post-post-apocalyptic future, where they rebuilt.
And one where it was actully a dimension hop, with a joke of the real future of the The Flintstones having flying cyborg dinosaur in place of all the robots and still all the rock puns.