Here is the information on Sailor Chibi Chibi Moon. "Chibi Chibi!"
The story of Sailor Chibi Chibi Moon slightly runs into the story of Sailor Galaxia. When the force known as Chaos appeared in the galaxy to engulf everything in darkness, the strongest (and most arrogant) soldier Sailor Galaxia set out to destroy it. However, she found the only way to stop Chaos was to absorb it into her own body. Yet, Galaxia was not able to control Chaos, and it possessed her body. As a last resort, she sent out a light of hope (her starseed) out into the universe hoping someone would take care of it, and eventually stop the monster she would become. This light of hope is otherwise known as, Chibi Chibi. 
Anime
Sailor Galaxia became a formidable foe, conquering almost the entire galaxy with her animates. Around this time, Chibi Chibi fell into the care of Usagi and the others. No one could really understand who or what Chibi Chibi was, for the only thing she could say was in fact "Chibi Chibi!" This kawaii little 2 year old had a way of getting in and out of trouble... Eventually it was revealed that she could transform into Sailor Chibi Chibi Moon. She never had her own henshin, attacks, or weapons, but she gave Eternal Sailor Moon new power, and transformed into a sword to fight Galaxia.
At the end of this battle, Sailor Chibi Chibi Moon dies.
Manga
Chibi Chibi has a different story in the manga, even though she appears in the same manner as she did in the anime. She is also Sailor Chibi Chibi Moon, however, her future self is Sailor Cosmos. In the future, the way Sailor Moon defeated Chaos is my jumping into Caulderon, the river of birth and rejuvenation, and sealing it there. However, there was still a bit of Chaos left in Caulderon that grew into a great enemy that caused much destruction. Therefore, Sailor Cosmos went back into the past as Sailor Chibi Chibi Moon to make Sailor Moon destroy Caulderon. The threat of Chaos was then defeated in the future.
Sailor Chibi Chibi Moon's Gallery
