Chibi Chibi

ちびちび

Chibi Chibi seems to be around two years old and cannot really speak yet, although she knows a few basic words and enjoys repeating what others say. In the manga, she mostly mimics the endings of other people's sentences; in the anime, she mostly says "chibi". Her red hair is always styled in two heart-shaped odango with small ringlets sticking out from the sides, mirroring the hairstyle of the protagonist, Usagi Tsukino.
In each series, Chibi Chibi immediately attaches herself to Usagi's family, whose memories are altered so that they believe her to be their youngest child—almost exactly what Chibiusa did upon her first appearance. Once again, only Usagi's memory remains intact, and because Chibi Chibi possesses the conversational skills of a toddler, the Senshi are unable to question her.
Chibi Chibi eventually transforms, using her own power, into a Sailor Senshi. In the manga, she is simply named Sailor Chibi Chibi, while in the anime, she is called Sailor Chibi Chibi Moon. In the manga, Chibi Chibi transforms by shouting the words "ChibiChibi Crystal Power! Make Up!". This transformation is never shown on screen in the anime.
The truth of Chibi Chibi's identity is very different in the manga from what it is in the anime, largely because the two series were being produced at roughly the same time.
In the manga:

Spoiler