There are many differences in the history of the character of Washu in the OVAs and TV series. Most notably, in the OVA series she is credited with the creation of Ryoko, Ryo-Ohki, and Kagato's ship, Soja. She was Kagato's teacher before he turned to evil, has had a husband and child, and is one of the three goddesses (this story arc has not yet been concluded, pending the release of the third OVA series). She has no memory before 20,000 years ago when she was reborn as a child (her previous self being sealed up in the three gems that Ryoko once possessed).

The history of Washu in the TV series is not so deeply explored. In the first ("Tenchi Universe"), she is a professor at the Galactic Academy, exiled 700 years previously because her work was considered too dangerous. Since then, she had been imprisoned in a cave on Earth until Ryoko freed her. In the second series ("Tenchi in Tokyo"), she is a renegade scientist who was hired by Ryoko to help her steal a precious artefact from planet Jurai.

However, in all incarnations she is considered the finest scientific mind in the galaxy, if not the universe. Her expansive laboratory, covering five whole planets, is set up in a closet under the stairs in the Masaki home (although this is actually only the doorway to some other dimension where the lab itself resides).

Some of her more interesting facets are only explored in the second and third OVA series. In series two we are given some explanation as to why she chose to remain as a young girl. A traumatic event in her young life lead her to turn her back on the world of adults, and never grow old. In the third series we learn of her true nature and how she came into being 20,000 years earlier.

In the original concept for Tenchi Muyo, Washu was supposed to have two forms; an illusory male form, and her true female form. She/he was also intended as the lead villain in the original OVA series, and to have killed Tenchi at the end of the fifth episode. OVA Kagato is, essentially, a logical progression of this idea, since he is a student of Washu.

* Birthdays indicated are taken from Japanese seiyuu's birthday, as opposed to any official date.