She only has had her cabbit form for about a year. Ryo-ohki acquired this form after her original form (a spaceship) was destroyed in a battle with Ayeka's Ryu-oh (another spaceship). Ryo-ohki still possesses the ability to transform into her spaceship form due to the crystal in her forehead. There is a poetic justice in this since the original Ryu-oh also ends up being destroyed, but later there is a relationship between Ryo-ohki (in cabbit form) and Ryu-oh (in tree form) to the point where they can combine to form a super spaceship with Ryo-ohki's firepower combined with Ryu-oh's ability to create the Light Hawk Wings as all high-generation Juraian ships can. Later, she also acquires a female humanoid form when she assimilated once again with the "Mass" in order to protect Tenchi who was threatened by the out-of-control "Mass".
Ryo-ohki's history is closely linked to that of Ryoko. Ryo-ohki served as Ryoko's spaceship in various raids on planets when both of them were originally under the control of Kagato after Kagato betrayed Washu. Ryo-ohki assisted Ryoko in capturing artifacts for Kagato and destroying many worlds in the process. Then, about 700 years from the present, they both attacked Jurai in an attempt to capture the sword Tenchiken as well as Tsunami, the most powerful Juraian tree who was also a deity. However, they failed to capture either, and they were pursued to Earth by the First Crown Prince of Jurai, Yousho, who severely damaged Ryo-ohki with his ship Funaho and went on to defeat Ryoko and imprison her in a nearby cave. Ryoko was set free from the cave by Tenchi, the grandson of Yousho, 700 years later, and Ryoko was once again summoned, this time to battle Ayeka, the First Crown Princess of Jurai and Yousho's half-sister. The ship Ryo-ohki was destroyed in this fight, but the ship was able to reproduce itself in the form Ryo-ohki takes most of the time...that of an adorable cabbit.
Ryo-ohki shares Ryoko's ability to phase through solid objects and is also mind-linked with Ryoko, meaning that whatever Ryo-ohki sees or hears, Ryoko can gain access to. Ryo-ohki is alsoable to fire a beam from the crystal on her forehead, but only for defensive purposes. When in cabbit form, Ryo-ohki can lift objects or people that are many times heavier than she is by levitating them, although using this ability is very taxing on Ryo-ohki.
Ryo-ohki gets along really well with everyone. Even Ayeka, who does not get along with Ryoko most of the time, likes Ryo-ohki especially after Ryo-ohki kept her company when she thought she had lost everything after the loss of Ryu-oh. Sasami and Ryo-ohki are especially close (Sasami is Ayeka's little sister). The two are best friends, and at times they seem almost inseparable. Ryo-ohki goes out of her way to try to please everyone, whether it's delivering mail for Ayeka, fishing for Ryoko, or helping Tenchi harvest carrots. Ryo-ohki seems obsessed with carrots, and there are few things that Ryo-ohki would not do just to be able to have a carrot. Ryo-ohki is a great addition to the Tenchi family, and she just goes to show that sometimes powerful friends are found in the cutest of packages.
