Dr. Clay (Ｄｒ．クレイ Dokutā Kurei?) is the main antagonist from the second Tenchi Muyo! OVA series.
He was a colleague of Washu, before her capture by Kagato, and was highly jealous of her superior intelligence. The two, at one point, competed for the Jurai Science Academy's directors chair, but Washu won out (Clay would claim Washu sabotaged his chances by substituting a raunchy porn tape for his presentation, while Washu claims that it was because Doctor Clay was a "bastard"). As a result, Clay had to settle for the post of head of the graduate school.
At some point, he came into the employ of a mysterious and powerful extra-dimensional being known as Lady Tokimi, who allowed him to bring Washu to her, in exchange for the rule of a single galaxy.
To this end, Clay had his creation Zero replace Ryoko, copying her form, powers, and even memories. However, Zero also did something she was supposed to be incapable of: she copied Ryoko's emotions, which led her to defy her creator.
He has great tendency of physically labeling or marking his favorite material objects with his own initial "ク" (ku) logo, including his own hat. Having everything of his favorite objects being marked with his own logo is subsequently his own downfall; having Washu finding his logo on Zero's (synthetic) buttocks and revealing the location of his spaceship's womanly bridge.
In the end, Clay was arrested by Mihoshi, and the dying Zero was merged with Ryoko. Sometime after his arrest, Tokimi's servant D3 modified the memories of both Clay and Zero (while being merged with Ryoko?) to conceal Tokimi's existence.
As for the character design of Dr. Clay, his overall shape of his head resembles as an octopus (His hair has eight long curls). Washu tends to exclaims "Octopus Head" to him as some form of insult.
- When Washu exclaims "You octopus-head" to Dr. Clay in the Japanese version, the English version replaced Washu's line with "You idiot" instead. Reasons for this change in the dubbings is unknown.