OC Senshi are very common in fanart and fanfiction. As is with most creative talents, some are well-written and well-drawn, and some are…not. “Sailor Earth” and “Sailor Sun” were easily the most common OC Senshi names. It’s saying something that those two Senshi names were a cliche back in the *90s*. Many fans often react negatively to Sun/Earth OCs simply because the concept is so overdone. Sailor Earth is such a cliche that there is even a TV Trope named after her.
When the writer/artist uses an already created character for Sailor Earth, rather than an original one, it’s almost always Naru Osaka. I imagine this is based on the series’ tendency to make every single female character significant to the story in some way. But Naru was always intended to be a regular Earth civilian – someone who Usagi could tie herself to beyond her Senshi duties. One of her most important character traits is that she probably knows that Usagi is Sailor Moon, doesn’t let on that she knows, and totally accepts that Usagi has responsibilities she cannot share with everyone. If she were to discover that she is a Senshi, that destroys that character trait.
When it’s an original character who turns out to be Sailor Earth, it’s conveniently someone related to an already existing character, with the “long lost sibling” thing thrown in just to make the cliche storm even worse. The usual targets are Usagi, Mamoru, Chibiusa or Minako. And these characters are very often referred to as “Mary Sues.” For those unfamiliar with the term, it refers to a fanfic character who is basically a self-insert of the creator, who is usually heavily based on the creator, overly significant to the story, implausibly powerful, and has captured the attentions of all of the existing characters. It’s often very young fans who make the mistake of writing a Mary Sue character, so it’s important to give constructive feedback rather than attack with hostility.
The real problem with the Sailor Earth cliche is that there already IS a Sailor Earth, and he’s been there since the first episode. “Mamoru Chiba” is a loose pun meaning “Protector of Earth.” And, as we find out in the Stars arc, he carries the Sailor Crystal/Star Seed of Earth. Although he doesn’t wear a uniform (sorry for the mental picture there) he is functionally Sailor Earth. And really, this should have been obvious. He’s the PRINCE OF EARTH.
The English dub barely kept any of the name meaning puns, so if you’d only ever seen the English version, “Darien,” which means “gift,” doesn’t really give that clue. The TokyoPop translation of the manga tried to incorporate the name pun a little bit by giving him the last name “Shields.”
What of Sailor Sun? Well, it’s not too far fetched for a star to have a Senshi, as indicated by the Sailor Starlights. There are canonical Senshi for asteroids as well. (It’s plausible that any heavenly body could theoretically have its own Sailor Senshi.) But we get the same problems with the Sailor Sun thing as we get with Sailor Earth. And on top of that, Sailor Sun tends to be written as even more ludicrously powerful and with the “evil twin” cliche. It can get a little cringeworthy.
There is no canonical Sailor Sun in the series as there was for Sailor Earth, but we do get something close, if you know your mythology. As you may already know, there is a TON of Japanese, Roman and Greek mythology interwoven in the series. The character of Pegasus is already based on a mythical beast from Greek mythology, but his real name, Helios, also comes from Greek mythology. Helios was the Titan God of the Sun in Greek Mythology. The original 12 Titans were descended from Uranus and Gaia. Helios is the son of Hyperion, God of “Watchfulness, Wisdom and Light.” Hyperion is relatively obscure compared to his son, and his brother Cronus.
As Greek mythology is thousands of years old and primarily relied on oral communication, there was a lot of muddling between the stories of Helios and Apollo. Apollo is the son of Zeus, and is also a Greek God of the Sun. Because the two Gods have very different origins, scholars insist that they should be considered separate entities, despite their similar divine dominions. I bring up Apollo because you may have heard of his twin sister, the Goddess of the Moon – Artemis.
And, as one final tie to Greek Mythology, the place of dreams where (Sailor Moon’s) Helios resides is called Elysian, which is the name for one of the Greek mythological concepts for the afterlife. It eventually would somewhat resemble the Judeo-Christian concept of Heaven, as it was said to be the place where the chosen of the Gods (the righteous, heroic etc) would spend their afterlife. Elysian is one of the levels of Hades, with Tartarus being the level where the evil and wicked people went. The entirety of Hades tends to get confused with the Judeo-Christian concept of Hell. (The God Hades tends to be associated with the Devil as well, despite being a neutral rather than evil deity)
Naoko Takeuchi was very careful about the names of her characters. Every single character’s name held some sort of significance, whether it be a pun on their powers, a reference to her training in chemistry, or an allusion to mythology. In this sense, while I can definitively say that there IS a Sailor Earth, I think it is safe to say that Helios was meant to occupy a “Sailor Sun” role, although he did not have a Sailor Crystal. Since he is also canonically tied to both Neo-Queen Serenity, Princess Lady Serenity, and King Endymion through his role as the protector of Elysian, it makes sense that the Moon, Earth and Sun would be connected in this way. When there are theoretically millions of Sailor Senshi out there, an oversight like not having Senshi for “Earth” and “Sun” would seem rather large…unless you realize that they were there all along.
Scan from Artbook IV by SailorMusic.Net.