Every planet has some aliens on it. That’s the rule.

Seal People:

These ancient enemies* of the Atlanteans become the allies of the evil Daka after he usurps the throne of Atlantis. Sadly they do not figure into modern day Marvel Comics continuity, as there being an intelligent species native to Antarctica would really shake up the ol’ geopolitical arena. (Marvel Mystery Comics v1 024, 1941)

*For “ancient enemies,” the Seal People do seem to be suspiciously nice and helpful – perhaps this is just further evidence for the Atlantean tendency to pick fights with other nations.

The Seal People return in Human Torch v1 005b as part of a coalition of undersea races uniting against the surface world. They are joined by the Walrus Men (presumably a related species) and the Shark Men, both of which groups are unnamed in the issue and not referenced again for decades later.

Moon-Men:

When weird tides start afflicting the Earth to the extent that humanity’s survival is in question, heroic scientist Dr X acts in the only way he knows how: load his niece Cynthia and her boyfriend Bob into a teleporter and blast them to the Moon to look for answers. And answers they find, in the form of a horde of big-headed Moon-Men who immediately capture them and hustle them before their king, who in turn hands them over to their chief scientist Goli to explain the plan: smash up the Earth until the human race is too weakened to resist a lunar invasion. Just why are Moon people so frequently intent on invading the Earth anyway? Surely the gravity would be hell for them, right?

Luckily for Cynthia and Bob and also humanity, the Moon-Men have the kind of sexual dimorphism that means that while the males are all weird little gnomes the females of the species are in fact hot babes who are capable of feeling sexual attraction to humans, as the Moon-Princess does toward Bob. This inspires her to set the humans free, which in turn allows them to blow up Goli’s lab and escape back to the loving arms of Dr X. (Startling Comics 004, 1940)

Moon People:

These very eerie-looking Moon People do not, in fact want to conquer the Earth. Instead, they merely want a load of human slaves, and they are lending their technological might to the very Hitlerian Boris Thorax so that he can conquer the Earth and then provide them to them. Though Rex Dexter of Mars prevents the planetoid Tarsis from smashing into the inhabited portion of the planet and kills Thorax with a single mighty punch, the Moon People get off without even a sternly worded letter. (Mystery Men Comics 001, 1939)

Moonmen:

This lack of reprisal seems to have emboldened the peoples of the Moon, because not one year later (at least, in our time frame – who knows how long has elapsed in the far future world of Rex Dexter) we find the Earth being menaced by Lunar technology once more. This time, a mysterious ray is causing humans to go berserk and attack one another in classic lunatic fashion. Adding insult to injury, the Earth ships that are sent to investigate possible sources of this phenomenon are destroyed by a powerful death ray as they approach the Moon. Finally, Rex Dexter agrees to help out and is successful in landing on the satellite’s dark side, where he encounters the hapless former inhabitants of the light side, who have long since been enslaved and exiled by their more warlike dark side counterparts. These Dark Side Moonmen are of course also responsible for the ongoing attack on the Earth.

Rex and his Earth forces are able to clean up the Moonmen with ease, though a group of them do escape in his ship, necessitating its destruction. As always, I appreciate when two intelligent species from the same planet look like they plausibly belong to the same evolutionary tree, though what evolutionary pressures created a race of Mean Jocks and one of Hapless Nerds in such close proximity is a real mystery.

Not only is the Earth saved, but by destroying so many of the Dark Side forces, Rex has freed the Light Side Moonmen from bondage and allowed them to reclaim their homeland. Hooray! (Mystery Men Comics 014, 1940)