Rennie is an interesting character. When she first appeared she fell rite out of the sky (literally) interrupting a "moment" between Derian and Serenea. After Serenea gains conciensness, Rennie demands the silver crystal from her. This is a typical statement from her, since it is her mission. Rennie was sent back the to the past  by Sailor Pluto to get the Silver Crystal to save her mother Neo-Queen Serenity, (who in case you didn't know is Sailor Moon.). Rennie needs the crystal to save her mother. She goes threw an number of stages trying to figure out who has the crystal, Amy, Ray, Lita, and so on and so on, never thinking that Serena has it because "she is to much of a ditz". During  this time she is being chased by the sisters of The Black Moon, who are also trying to find the crystal, and her AND take over present day Tokyo. Are you confused yet?

 Rennie is the future daughter of Serena and Derian (yes folks they do get back together) In the future there is some kind of accident that causes Neo-Queen Serenity ( Rennie's Mom) to lose the crystal and become in great danger. Not only that but they are also fighting a battle against The Black Moon. Fearing for her daughter Neo-Queen Serenity sends her daughter into the "safer" past to find the crystal, and save the future. Rennie finds Serena, (the past one) and goes and lives with her family. They seriously get on each others nerves.
 

Name: Serenea (Rennie), Small Lady. Japanese Name: Chibi Usa     Blood type: O - Birthday: June 30 Birthstone: pearl Age: 9 Sign: Cancer Favorite Color: red and pink Favorite Food: pudding Least Favorite Food: carrots Favorite Subject: drawing

Worst Subject: Languages Dream: becoming a lady Favorite Gemstone: Diamond  School: Minatoku Juuban elementary school Hobbies: collecting rabbit paraphernalia Strong points: getting people to give her things, getting people to do what she wants Has trouble with: taking care of the house, thunderstorms     Powers: Pink Sugar Heart Attack, Moon Gorgeous  Meditation, Double Moon Kick, also she has the power of the Silver Crystal

Rennie also meats Sailor Moon, (she doesn't find out it Serena until later) and believes deeply in her and asks her to help her mother, and Sailor Moon says yes (not knowing who her mother really is)  So after  some time Serena figures out who Rennie is, but doesn't say anything, and Rennie figures out who Sailor Moon is, and is very surprised. So now Sailor moon has to some who bring Rennie back to the future and save her mother

    Now like i said, Rennie was also being chased by the Sisters of the Black Moon. Sailor Moon brought them all back to the good side and destroyed Rubes. Then, after defeating all of the Black moon,  Sailor Moon sends Rennie  home.

    Later, Neo-Queen Serenity sends Rennie back to the past again to learn to be Sailor Moon (who better to tech you to be Sailor Moon then Sailor Moon herself) Anyway, her best friend is Hotaru-chan (Sailor Saturn). She is also GOOD friends (A little crush) with the Pegasus named Helios, a horse with wings. She is called Rennie  BY EVERYONE ... except, Setsuna and Diana who call her Small Lady, and in return Rennie calls Pluto, 'Puu'. As a Sailor Scout, Sailor Chibi Moon is .. anoying and whinny. She is often times rude and unfair to her mother Serena.
 

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Moon Prism Power, Make Up

Rennie says this to turn into Sailor Chibi Moon.
 
Moon Crisis Power, Make Up
Rennie says this to turn into Super Sailor Chibi Moon. 
 
Luna-P Henge/ Kitty Power
When she bounces/dribbles the Luna-P ball around and throws it in the air and she can make the ball transform into objects. She says, "Kitty Magic!" The ball bounces high into the air. then, the ball turns into whatever Rennie wants. she can also use it to call Sailor Pluto into the Future.
Pink Sugar Heart Attack

Sailor Chibi Moon uses a special stick to blast her enemy with a whin of hearts.
Twinkle Yell

Sailor Chibi Moon says this to call the Pegasus.
Crystal Key
Rennie uses a small key that Pluto gave her to go home to the future. She has tried it twice in the american version, but it hasn't worked.