Earth-S was very unique in the midst of the Multiverse. For one thing, there was no Superman, Batman, Wonder Woman or derivatives thereof. Indeed there were analogues to each of these, and other superheroes and heroines, both in the golden age starting in the 1940's like Earth-Two and the silver age 1970's such as on Earth-One. Nevertheless, there was also a lack of scientific principals, as this particular universe's particular laws of physics almost lent themselves as much to the whimsical as the wonderful. But that wasn't all that made it stand apart from the rest.
On this world, the greatest superhero team that ever existed wasn't the Justice League or the Justice Society, no Justice Alliance nor Freedom Brigade. Not even a Crime Syndicate... well okay there was the Monster Society of Evil but, as it was, they were evil if not persistent. However, on Earth-S, their premier team was a family! Yes, the Marvel Family, consisting of Captain Marvel along with his sister, his best friend, three namesakes, a lovable old fraud and the elder guardian who empowered them all.
That's not to say this world didn't have their share of costumed crusaders. Indeed, Bulletman and Bulletgirl were as prolific as protectors as were Hawkman and Hawkgirl. Mister Scarlet and Pinky were as gifted a dynamic duo as were Batman and Robin. Spy Smasher was evenly matched with Sandman, as was Minute Man with the Star-Spangled Kid. That's just the tip of the iceburg.
And indeed, these various heroes teamed up informally throughout the years at social events, and they were all stuck together in Suspendium thanks to the machinations of Doctor Sivana after the Captain's long time friends showed up to support a ceremony in his and his Family's honor. Eventually, they would team up, well most of them, to form Shazam's Squadron of Justice. Still, this was a one-and-done scenario, as most of the members then proceeded to retire or at least semi-retire. Except for the Marvels.
Still, this world was well protected, so much so that none of the various incarnations of the Monster Society were able to vanquish good from that planet. And so it would remain, until the Crisis on Infinite Earths. Or, in at least one timeline, into the uncharted future.