Seven hundred years ago, a certain genius professor was exiled for creating weapons of mass destruction- but even that incident didn’t put Washu off of her beloved science. Even now, her latest and greatest experiment is proceeding as planned.
Whilst Washu works hard in her lab, Ryoko and Ayeka are enjoying a more relaxing pastime- watching their favourite soap opera. Unfortunately, just as the show is getting to its juiciest part, someone changes the channel. Turning around in annoyance, Ryoko and Ayeka see that the culprit is Mihoshi. The GP officer came over to invite herself to lunch, but, to her disappointment, everyone in the Masaki house ate a while ago.
Everyone, that is, except Washu, who has so far missed both breakfast and lunch. Sasami is starting to get worried, and so Tenchi decides to go down to the lab and find out what Washu has been doing.
Washu is delighted to have someone to show off her latest project to, and quickly takes Tenchi over to see what she has been working on- Mecha-Washu. Like the name suggests, Mecha-Washu is a mechanical copy of Washu, designed to help the genius scientist catch up on her work after her seven hundred years in exile. Washu has been working all night to physically complete Mecha-Washu, and now only one thing remains- to copy her own mental data to the robot. After all, two geniuses are better than one, right?
Unfortunately for Washu, an unknown element has entered the equation. Mihoshi has entered the lab, and, where she goes, disaster follows close behind. Stepping into the mind data duplication tube, Washu asks Tenchi to switch it on, but in an attempt to be helpful, Mihoshi steps up to the control panel instead. Soon, Mihoshi is pressing every button in sight, and in short order, the tubes containing both Washu and Mecha Washu are destroyed in a Mihoshi-generated explosion.
Somehow, both Washu and Mecha-Washu survive the explosion, and when Mecha Washu activates, it looks like the mind data transfer was successful as well. However, something isn’t quite right about Mecha Washu- her eyes, hairstyle and mannerisms all seem to resemble those of a certain clumsy GP officer. Realising that something must have gone wrong, Washu examines the remains of the mind data transfer tube, only to notice one of Mihoshi’s hairs caught in the door. Mihoshi’s data was input as well, and somehow, only a single ‘dimwit’ hair was able to override Washu’s genius mind.
After bemoaning the way her wonderful experiment has gone so disastrously wrong, Washu finally realises that the robot has disappeared, and she, Tenchi and Mihoshi set out to track it. Driven by Mihoshi’s mind, Mecha-Washu has cleaned out the fridge and gone to join Ryoko and Ayeka in front of the television- only to leave after their soap opera is interrupted once again, this time by a news bulletin about a bank robbery.
Believing herself to be a GP officer, Mecha-Washu plans to head over and stop the robbery, and when Washu and the others try to stop her, she decides to punish them for obstructing the course of justice. She tries to knock Washu down by shooting her forearm at them in a “Mecha-Washu Punch”, but her control over the mechanism is just as bad as Mihoshi’s would be. Flying up into the air, the arm misses Washu and knocks Mihoshi out instead.
As Mecha-Washu starts attacking Washu with her “Mecha-Washu Beam”, Ryoko and Ayeka come outside to see what could be making so much noise that they can no longer hear the television. Unfortunately for them, Ryoko and Ayeka succeed in catching the attention of Mecha-Washu, and she accidentally catches them in her next blast.
Realising that she will need her very best tactics to defeat the overpowered robot, Washu decides to put one of her favourite ploys into effect- Operation Volleyball. She materialises a volleyball net and a very special ball- one that explodes when dropped. Tossing the ball into the air, Washu attempts to send it over the net to Mecha-Washu, but she is so out of practice that she manages to send it sailing in the opposite direction, towards Ryoko and Ayeka.
Ryoko quickly pushes Ayeka out into the ball’s path, but much to her dismay, the princess just punts it over to her anyway. Ryoko quickly generates a force shield that repels the ball and knocks it away- right towards Tenchi. Reacting quickly, Tenchi punts the ball over the Mecha-Washu, who proves to be a much better volleyball player than her creator. Mecha-Washu expertly deflects the ball away to the vegetable garden, where it finally explodes- taking the entire crop of Ryo-Ohki’s beloved carrots with it.
With no other options left, Washu realises that she will have to use Mecha-Washu’s self-destruct to destroy the robot she worked so hard on. Using her computer, Washu activates the self-destruct, but even though Mecha-Washu’s body is blown up, her head somehow survives. As it flies through the air, the Mecha-Washu head calls for the spare body Washu was keeping down in the lab. The spare obediently comes outside, and, before anyone can stop it, it attaches Mecha-Washu’s head to its neck.
As Mecha-Washu begins firing even more beams, Washu realises the situation is hopeless- this spare body doesn’t even have a self-destruct. Fortunately, help is at hand- Kiyone has come over to look for Mihoshi, and no one knows Mihoshi’s mind like she does, no matter which body it is in.
After the others fill her in on the situation, Kiyone quickly glances at her watch and comes up with her solution. Calling to Mihoshi, she tells her partner that she’d better get inside- or she’ll miss her favourite TV show. Seeing Mihoshi rush indoors, Mecha-Washu quickly realises that she had better follow, or she will miss the show as well.
With Mihoshi and Mecha-Washu engrossed in their favourite anime, all is finally quiet. As the only one a Mihoshi mind would pay attention to, Kiyone is easily able to get Mecha-Washu to hold still whilst she finds the switch at the back of the robot’s neck, and finally switches it off. Kiyone may be far from proud of her extensive knowledge of Mihoshi’s mind, but thanks to that knowledge, the Mecha-Washu is finally over.
Not one to be deterred by a little setback like the whole Mecha-Washu incident, Washu decides to give the process another go, by taking even greater care with the creation of Mecha Washu II. Unfortunately, when a proud Washu unveils Mecha Washu II to the others, it becomes clear that something isn’t right with this one either- it is acting just like Ryo-Ohki. The little cabbit was playing down in the mind transfer tube, and somehow even her cabbit mind was able to override Washu’s data. It looks like poor Washu won’t be getting her genius assistant after all.