Scientific genious Washu
Washu is the mad scientist that created Ryoko and Ryo-Ohki. Washu is one of those people in the universe that you just don't mess with. She always seems to be ready for whatever happens to be in her way. Some of her inventions include: Mecha-Washu, Mecha-Ryoko, The Galaxy Destroyer, A door that can connect any two points within space, and a machine that can generate any space/time that you want. All this and they still had to buy a karaoke machine.
Washu is one of the three goddess in the Tenchi Universe. She was also the most powerful. Why do I say was? Over 20,000 years ago, Washu's powers and memories were sealed away into three gems. This was the reason that she created Ryoko. Ryoko is capable of channeling this power given that she has all three gems. During the process of creating Ryoko one of her assistants named Yakage, who was charged with creating the perfect sworrd for Ryoko, stole some of the earliest cells and made his own Ryoko. Her name is Minagi and appears in the No Need For Tenchi manga. After the creation of Ryoko, Kagato trapped Washu within her own invention and abused Ryoko's powers for his own evil purposes.
Washu remained trapped within a large crystal within the mirror dimension of Soja, Kagato's ship which was invented by Washu as well. Washu was released when Kagato came to earth to reclaim Ryoko. Thinking Tenchi dead the girls go to avenge Tenchi and Mihoshi accidentally releases Washu.
Washu's subspace lab is actually located on five seperate planets. These plantets are interconnected using interdimensional wormholes all connected to the main lab which is the one she appears in most frequently. The labs include a supercomputer lab, a biology lab, a lab for extracting "samples", a cybernetics core, and the main lab that contains the shell created by Kagato for Tsunami.
She maintains the appearance of a 12 year old because when she was young (20,000 years ago) she had a child. But it was taken from her because of the father's social status. Washu figured that if she took on the appearance of a 12 year old , such things wouldn't matter. At the end of OAV episode 8 Washu "Grew up" and offered to have another child if it was Tenchi's. This offer was not met well with Ayeka and Ryoko. ^_^