A Look at the Small Rabbit

ChibiUsa ... the kawaii pink-haired princess of Crystal Tokyo, about 1,000 years into the future. Confused? Let's rewind.
  ChibiUsa first made her introduction in SailorMoon R. Usagi (SailorMoon) and Mamoru (TuxedoKamen) were kissing on the dock by a lake, when the strange girl toppled from the sky with her Luna-P Ball, knocking Usagi flat and stealing her kiss with Mamoro. Immediately, she demanded the Ginzuishou (Silver Crystal) and shot Usagi in the head with a toy gun. She then introduced herself as Usagi and disappeared ... temporarily ...
   Usagi was shocked to find ChibiUsa in her home later that day, as her family referred to her as a cousin. Usagi and the other senshi tried to figure out where she was from.
   ChibiUsa (as she goes by to avoid confusion) was from Crystal Tokyo in the 30th century. The kingdom had been under an attack by the Black Moon family, and ChibiUsa's mother, actually future Usagi and Neo-Queen Serenity, had been trapped. The princess turned to Puu (SailorPluto) for help. She was given a time key to travel back into present Tokyo and find the Ginzuishou to help her mother, since it had disappeared when ChibiUsa picked it up. ChibiUsa hypnotized Usagi's family into believing she was a relative, so she would have a place to stay as she searched for the Ginzuishou.
   Eventually, ChibiUsa took the senshi to the future with her, so they could defeat the Death Phantom, leader of the Black Moon family, and restore peace to Crystal Tokyo. During the time, ChibiUsa was infiltrated by the Death Phantom, and turned into an ally, Black Lady. She was able to turn back to ChibiUsa with the help of Usagi and Mamoro and defeat the Death Phantom alongside SailorMoon. The season ended as ChibiUsa went back home to the future.

   In SailorMoon S, ChibiUsa again returned to the 2oth century, to receive instruction as the senshi-in-training, SailorChibiMoon. ChibiUsa was an inportant part of the season because of her friendship with Tomoe Hotaru, the quiet possesse of the spirit of SailorSaturn. In SailorMoon S, ChibiUsa struggles to keep the outer scouts from killing Hotaru whose destructive subconscious could awaken and be the cause of the end of the world. ChibiUsa's friendship and faith is so strong, that she goes to all risks to protect Hotaru, threatening her life and friendship with Setsuna. In this saga, ChibiUsa still possesses most of her traits, some of which are pestering and arguing with Usagi. But she is more mature and understanding, not to mention nicer. ^_^

  SuperS focused on ChibiUsa, as she made friends with a fleeting Pegasus named Helios. Helios is the ruler of a land called Elysion, and took the form of a Pegasus to hide in ChibiUsa's dream mirror for safety from Queen Neherenia. Helios eventually becomes an aid to the sailor senshi and gives ChibiUsa a new attack, Twinkle Yell. ChibiUsa and Helios fall in love sometime during this timeline, and ChibiUsa becomes an official Sailor Senshi, SuperSailorChibiMoon.

   ChibiUsa returned to the future shortly after the start of SailorStars. She had almost died, as Mamoro was almost taken in the battle with the Neherenia, leader of the DeadMoon Circus. No Mamoro = no ChibiUsa, because he's her father from the future, but luckily, they both survived, and ChibiUsa was able to return to the future in one piece.
   In the manga, ChibiUsa stayed in present Tokyo in the last saga, with her current form, SailorStarChibiMoon.