After a new experiment goes haywire at the science convention, all of Dr. Wakeman's XJ robots and other inventions mysteriously begin to run amok and turn on her — even Jenny herself! Who is responsible for this heinous crime?
At a science fair, Dr. Wakeman's garbage-consuming experiment suddenly goes berserk and destroys the fair. Embarrassed and confused, she and Jenny fly home and try to forget everything with a good night's sleep.
Battle with XJ-1
Dr. Wakeman wakes up in the middle of the night and sees XJ-1 sitting innocently in front of her, as she was somehow activated. Nora questions her activation, but XJ-1 then unexpectedly and angrily vomits oil on her and shoves herself into Dr. Wakeman's mouth as if to choke her. Wakeman forces her out and smashes XJ-1 against the wall, cracking her like an egg. Deeply disturbed by XJ-1’s atypically violent and vicious behavior, she questions what could possibly be wrong with her.
Battle with XJ-2
Suddenly, XJ-2 appears and attacks Nora using her plasma beams. Terrified, Nora runs from her and tries to hide in various closets (one in which her pet tiger sleeps in), but cannot evade XJ-2’s relentless barrage of laser blasts. Soon Jenny shows up, having heard the ruckus. She opens a door and accidentally knocks XJ-2 into a closet full of Tuck’s stored fireworks. Firing a laser beam in the closet full of explosives results in XJ-2 blowing up herself and half the house. Dr. Wakeman frantically tells Jenny that XJs-1 and 2 are malfunctioning.
Battle with XJ-3
Tiny XJ-3 then appears, with an unusual look of fury in her eye, and extends a scorpion-like tail which she uses to attempt to sting her creator. However, Jenny steps on and crushes XJ-3 before she can harm her mother. Deeply concerned, Jenny wonders why her sisters are attacking Dr. Wakeman, for even though they are kept in the cellar, it has never bothered them before.
Battle with XJ-4
XJ-4 appears and angrily sucks Nora into her built-in vacuum. Jenny pulls Nora out and XJ-4 “attacks” Jenny with spray bottles, a broom, and a feather duster. Jenny easily defeats her by punching her into Dr. Wakeman’s shoe closet, where XJ-4, being a compulsive neat-freak, cannot help herself and becomes distracted in sorting all of Nora’s shoes.
Wakeman tells Jenny to quickly turn off her other sisters before they all begin to attack. Jenny runs to the basement and shuts the remaining XJ-Sisters off, only to find out that XJ-5 somehow turned herself back on and escaped!
Battle with XJ-5
Back in the house, XJ-5 chases and attacks Dr. Wakeman. Nora grabs a fire extingusher to knock her back (all the while changing her radio stations, causing her to play different music). Jenny joins in and knocks XJ-5 to the ground, then punches her into the wall, breaking her (and causing her to play taps).
Wakeman and Jenny, extremely disturbed and perplexed by this mysterious phenomenon, decide to go to the convention center to figure out what the cause of the inventions going rouge could be, seeing as the problem started there with Wakeman’s garbage-consuming bot.
Battle with XJ-6
XJ-6 arrives, having chased Wakeman and Jenny to the convention center, and viciously attacks Jenny. While Jenny wrestles with her, XJ-6 vents out her vitriolic jealousy, contemptuously calling Jenny “mommy’s little favourite”. They begin to “sword fight” (with pipes) until Jenny defeats her.
Meanwhile, Nora fiddles with some left-over electronics in order to create a device to stop the attacking XJ-Sisters before it is too late.
Battle with XJ-7
XJ-7 then appears and forces Nora up against a wall, threatening to destroy her. But because of her lack of confidence and self-esteem, she just gives up and self-destructs without even trying to do any harm to her creator. XJ-7 then whines sadly that she cannot even self-destruct properly (as her head is still intact).
Jenny becomes anxious, wondering if they can figure out the problem before XJ-8 shows up, since XJ-8 is stronger than her. This leads Jenny to question why, to which Dr. Wakeman replies that she had to take out some of XJ-8's strength to leave room for XJ-9's teenage personality and sense of humor.
Battle with XJ-8
Unfortunately, XJ-8 arrives soon after, threatening to destroy Nora. Jenny fights her tougher sister, but XJ-8, being much bigger and bulkier, has the upper hand for a while.
Suddenly, Dr. Locus appears, ostentatiously claiming that he is the one responsible for forcing Nora’s inventions to turn against her — all thanks to his new and most powerful invention, a remote control with the power to control every invention on Earth.
After XJ-8 is finally defeated by Jenny, Dr. Locus uses the device again, zapping Jenny with it and forcing her to attack her mother.
Battle with XJ-9
Jenny tries to stop herself, but to no avail. Dr. Locus, determined to destroy Nora, laughs evilly and uses his remote to force Jenny to fire lasers and fling sawblades at her mother. Dr. Wakeman dashes about frantically, just barely avoiding Jenny’s uncontrollable attacks. Then, seeing an opportunity to save herself and Jenny, Nora quickly jumps in front of Dr. Locus and ducks just as Jenny fires another sawblade, which destroys the remote control device. Unfortunately, it seems as if this does not release Jenny from the evil invention’s control, and she extends her arms and grabs Nora in a stranglehold. It looks as if Jenny is about to finish off Nora, but then she suddenly hugs her mother lovingly and smiles. Since the remote was destroyed by Nora’s smart and fast thinking, Jenny was in fact freed from its control and had been pretending to attack her mom in the last few seconds to fool Dr. Locus. Locus yells in fury, claiming his invention is now garbage — and is then promptly gobbled up by Nora's trash eliminator.
Back at home, Dr. Wakeman and Jenny repair the XJ-Sisters, who are also back to normal and happy again. But Nora's tiger suddenly appears and swallows her whole, and Nora asks (from inside the tiger) if Jenny forgot to feed him...
- This is the very last segment aired on television before the series' cancellation.
- At the end, XJ-5 doesn't appear in the lab like her sisters (unless she was the first one to be repaired).
- At the very beginning of the episode, a reference to the classic Nicktoon Hey Arnold! is made. At the Invention Convention, a rotating football-shaped machine is displayed, and its inventor states clearly to the audience, “And as it turns, it looks like Arnold. Remember Arnold?”