In the first ever appearance of Superman, Action Comics #1 from DC Comics, Clark Kent's amazing strength and abilities are described with a "scientific explanation" that likens his physiology to that of Earth's insects. While it is now firmly established that Superman's array of powerful abilities comes from his Kryptonian physiology and exposure to Earth's red sun, Action Comics #1 previously compared his powers to bugs like ants and grasshoppers.
Superman, the "Man of Steel," has long been seen as the idealized version of man and hero, but in reality he is an unattainable goal, as is he is quite literally not from Earth. While Clark Kent may have been raised in Smallville by his quaint farmer parents Martha and Jonathan, he is undeniably an alien, an aspect of his character that has impacted the way Superman is viewed in the real world and in the fictional world of Earth-0.
Action Comics #1 was an anthology of stories, but the 13-page Superman story was written and illustrated by Jerry Siegel and Joe Shuster, respectively. Interestingly, Superman's first story did not name his home planet as Krypton and also did not offer up an explanation for his name of Clark Kent, both of which were established in later stories. Interrupting the story was a panel titled, "A Scientific Explanation Of Clark Kent's Amazing Strength" which established that Clark was an alien who, "Upon reaching maturity, the people of his race became gifted with titanic strength!" Perhaps thinking that people reading the comic would not even be able to conceptualize of a being so powerful, especially since Action Comics #1 is often viewed as the birth of modern superhero stories, Siegel and Shuster then went on to remind the readers that there are already creatures on Earth who possess similar abilities and strength.
Specifically, Superman's physical strength as compared to that of "the lowly ant" who "can support weights hundreds of times its own," as well as "the grasshopper" who "leaps what to man would be the space of several city blocks." Of course, bugs on their own are not intrinsically "creepy," but what is creepy is the dissociation this comparison makes between Clark Kent and that of humans. Nowadays, although everyone knows Superman is an alien, he tries his best to appear "acclimated" to human society. However, by directly comparing him to insects, and inviting readers to view him in a decidedly non-human context, his "alienness" is brought into clearer focus. In today's geopolitical climate this introduction could have been used as an interesting and timely allegory for immigration and assimilation into the United States, but at the time it seems as though it would just make it appear creepy that this bug-creature was attempting to trick people into thinking it was human. Also, this "scientific explanation" is really not all that "scientific" at the end of the day.
It seems as though DC Comics didn't realize how creepy this could be, seeing as just a few years later they literally turned Superman into a half-ant hybrid creature, caused by an exposure to a cloud of red kryptonite. Regardless, it appears like DC made the right choice in re-contextualizing Clark's powers as being intrinsically alien, instead of trying to push his abilities and being into a more human, Earth-bound context. Action Comics #1 is considered to be the most valuable comic issue in the entire world, but if you ever get your hands on a copy make sure to check out how DC Comics first "explained" Superman's powers, in a much creepier way than they probably intended!