When she first appeared in the series, Chibichibi appears to be about two years old, and cannot really talk yet. She usually imitates others, but mostly says “chibi”. Her names has two meanings, literally “small person” or “small child”, and as a pun meaning “making something last”.
She eventually transforms, under her own power, into a Sailor Soldier, Sailor Chibichibi. Although she does not to appear to have any attacks of her own, she does increase Sailor Moon’s power.
Oh wow, doesn’t Mikuro Nekomi make the perfect Chibichibi? I’m actually surprised to find cosplays of this character, so I had to feature it asap! Thanks again to Sophia for suggesting this!
Source: Mikuro Nekomi on World Cosplay