Is there a Sailor Mega Moon in the Sailor Moon series?

Answer 1

In the animated series, Sailor Moon has three distinct, separately-named forms: her original, which we see through Sailor Moon seasons 1-3, Super Sailor Moon, which we see in part of Season 3 and 4, and Eternal Sailor Moon, which we see in part of Season 4 and Season 5.

In the manga, a possible fourth form, separate from the "Sailor Moon" lineage, is Sailor Cosmos. Her origins are intentionally vague, even when series creator Takeuchi was asked about it in interviews; Chibiusa's Senshi Team from the future, the former Amazon Quartet, see Sailor Chibi-Chibi transform into this Sailor Cosmos, and ask if she is "the future Sailor Moon." Cosmos refers to herself as "the me from this time," and occasionally will use the third-person (Usagi, Eternal Sailor Moon)--not as one would if she were referring merely to her past self (me, the other me, my younger self, etc).

Furthermore, Cosmos doesn't undergo any harmful effects (such as the duplication paradox Sailor Moon and Neo Queen Serenity were warned of in their near-meeting toward the end of the Black Moon arc in the manga), which implies Cosmos, while she may be related to Usagi, Sailor Moon, or Serenity in some way, is not actually the same physical body that Usagi is.

It is worth noting that in the anime, Chibi-Chibi has an entirely different origin, although a shadowy form that resembles Sailor Cosmos was shown in the last episode. This form, however, is explicitly stated to be the ultimate form of Galaxia's Star Seed, the "Light of Hope," not Sailor Cosmos, whom Takeuchi said at Comic-Con

1998 that she was disappointed didn't appear in the anime.