Jack Constantine was a genius. Not as smart as Washu, but still a genius. He worked on the shrinker while forming his plan to capture Washu for Dr. Clay.
After Dr. Clay failed to get Washu for Lady Tokimi, he was sent to jail. 2 years later, Dr. Clay managed to escape with some help from Jack Constantine, who had heard about Dr. Clay. Dr. Clay's employer had been the high-enegy being known as Lady Tokimi, Jack knew. But Lady Tokimi has disappeared, even to the high-energy being known as D3. Not even D3 knew where Tokimi was, or why she hadn't come to visit him in 2 years. Of course, D3 really wasn't that worried. Lady Tokimi comes and goes at her own will. Jack Constantine had learned all this from D3 himself. D3 didn't order Jack to free Dr. Clay from prison. Jack was an escape artist and knew how to free Dr. Clay.
Dr. Clay wanted revenge on Washu. And he came up with a plan. 15,000 years ago, Washu had invented a robot programmed to kill her. Of course, Washu never finished the robot, but Dr. Clay did finish it without Washu's knowing. He called the robot "Dark Washu" and programmed it to kill anyone that got in its way to kill Washu. Dark Washu looked like Washu with a tan, but the robot could alter skin color. Dark Washu was also able to do all the things that Washu could do.
Jack Constantine came to Earth to deliver Dark Washu.
Dark Washu was currently on the shrinker. She was microscopic size, and would remain that way until Washu picked up the shrinker, or until Dr. Clay decided to activate it. Constantine was really making a "growth" fuction to the shrinker. Washu would have little time to use it when Dark Washu was activated.