This is Sailor Chibi Chibi. She falls out of the sky with an umbrella (kind of like Chibiusa in SMR). She then proceeds to Usagi's house and hypnotizes her family (again like Chibiusa in SMR). Luna thinks she could be Rini's future daughter. The senshi think she could be Usagi's second daughter, until Pluto says that the queen only has one child. So where did she come from??
(Anime Story)This story is long, but I will try to make it as brief as possible without confusing you. So pull up a chair, and relax...
There have always been sailor senshi in the universe, not just the ones we know about. They have participated in the Sailor Wars since the beginning of time. Sailor Galaxia was the strongest of them all, and watched over the Star Seeds. One day an evil force appeared to try and take over everything. Sailor Galaxia realized that she must stop it, so she decided to seal it in her body. Before she completed this task, she realized she would not survive this, so she sent her Light of Hope (her soul) out into the farthest reaches of the galaxy, praying that someone would watch over it to use against the evil that was possessing her. This Light of Hope is Chibi Chibi. She then fell into the care of Eternal Sailor Moon (Usagi), just as Sailor Galaxia had wanted.
But now Sailor Galaxia is the most powerful and most evil being in the universe, and the Inner senshi, outer senshi, and starlights must try to defeat her. In the last battle, when everyone but the starlights is dead, and Sailor Moon is lying there wrapped in ribbons (also dead) Chibi Chibi saves the day. She prays and brings Sailor Moon back to life, powers her up to Eternal Sailor Moon, and turns into a sword to defeat Galaxia. Alas, that sword breaks and she dies. But Sailor Moon defeats Chaos with her goodness, and the Good Sailor Galaxia is back along with everyone that died.