Chibiusa appears in the manga/ anime as a timetraveler, and it only gradually unfolds that she is, in fact, the daughter of Usagi and Mamoru. Chibiusa and Usagi naturally share many personality characteristics, as well as an astrological sign, but Chibiusa does seem naturally precocious compared to Usagi. The name "Chibiusa" in fact means "small Usagi".
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