Designed to be a general-purpose, if beautiful, tool for Kabapu, Ropponmatsu (Unit 1) excels in bomb-disposal. After failing in her first mission, she is given an additional form (Unit 2), that of a perky, young cat-girl. In the original manga, only one Ropponmatsu unit is active at any one time; the reason for this is later revealed to be that there is only one central "core" that is switched between the two bodies. Kabapu attests that the core contains the soul of the princess of the lost civilization of Solaria, and he has had the Ropponmatsu body created to house it as part of his plan to destroy all remaining traces of Solaria's technology. Conversely, the anime (produced before this revelation occurred in the manga), has the Ropponmatsus appearing as two distinct entities who frequently cooperate on important tasks. Although they have a tendency to be destroyed on their missions, Shiouji keeps a lot of spares, which play a large role in the penultimate episode of the series). The vast difference between the units leads to some tension between Kabapu and Shiouji: both incarnations of Ropponmatsu have a tendency to fail in the course of their duty, due either to extreme mass (Unit 1) or lack of appropriate functionality (Unit 2).
She is introduced in episode 3 as an assistant of sorts to the Female Informant from Episode 2. Much like her predecessor, she demands sex with either Rin or Mimi for information. Although, her first encounter with Mimi was less than romantic, by episode 4, they appear to have entered into some sort of relationship. After episode 4, she has apparently died.
Nodoka is Ranma's loving mother. She hasn't seen him and Genma in over a decade though, when they left on their training trip. Stating that a doting mother would hinder Ranma's training, Genma made a contract with her to raise Ranma as "man amongst men", and if he failed, he and Ranma were to commit seppuku. However, because Ranma's curse makes him a woman half the time, they spent most of Nodoka's appearances hiding from her as Ranko Tendo and her pet, Mr. Panda. Nodoka's heart was constantly broken by knowing that she wanted nothing more than to see her son again. Eventually in the manga, she did meet Ranma and Genma and discovers their curses. However, she was more accepting than they expected. Mostly because she eventually began to suspect that Ranma and Ranko were, in fact, the same person. (Wikipedia)
Mrs. Tendo is the mother of Kasumi, Nabiki, and Akane, and the wife of Soun. She passed away many years ago leaving Soun to raise the children. It is never said how she died, but the family still thinks of her lovingly. After Mrs. Tendo's death Kasumi assumed a more motherly role and helped with household duties. (Source: Rumic World)