Turncoats

Summary
After a new experiment goes haywire at the science convention, All of Dr. Blackman's HA robots and other inventions mysteriously begin to run amok and turn on her — even Alex himself! Who is responsible for this heinous crime?

Plot
At a science fair, Dr. Blackman's garbage-consuming experiment suddenly goes berserk and destroys the fair. Embarrassed and confused, she and Alex fly home and try to forget everything with a good night's sleep.

Battle with HA-1
Dr. Blackman wakes up in the middle of the night and sees HA-1 sitting innocently in front of her, as he was somehow activated. Susan questions his activation, but HA-1 then unexpectedly and angrily vomits oil on her and shoves himself into Dr. Blackman's mouth as if to choke him. Blackman forces him out and smashes HA-1 against the wall, cracking him like an egg. Deeply disturbed by HA-1's atypically violent and vicious behavior, she questions what could possibly go wrong with him.

Battle with HA-2
Suddenly, HA-2 appears and attacks Susan using his plasma beams. Terrified, Susan runs from him and tries to hide in various closets (one in which her pet tiger sleeps in), but cannot evade HA-2's relentless barrage of laser blasts. Soon Alex shows up, having heard the ruckus. He opens a door and accidentally knocks HA-2 into a closet full of Tuck's stored fireworks. Firing a laser beam in the closet full of explosives results in HA-2 blowing up himself and half the house. Dr. Blackman frantically tells Alex that HAs-1 and 2 are malfunctioning.

Battle with HA-3
Tiny HA-3 then appears, with an unusual look of fury in his eye, and extends a scorpion-like tail which he uses to attempt to sting his creator. However, Alex steps on and crushes HA-3 before he can harm his mother. Deeply concerned, Alex wonders why his brothers are attacking Dr. Blackman, for even though they are kept in the cellar, it has never bothered them before.

Battle with HA-4
HA-4 appears and angrily sucks Susan into his built-in vacuum. Alex pulls Susan out and HA-4 "attacks" Alex with spray bottles, a broom, and a feather duster. Alex easily defeats him by punching him into Dr. Blackman's shoe closet, where HA-4, being a compulsive neat-freak, cannot help himself and becomes distracted in sorting all of Susan's shoes.

Blackman tells Alex to quickly turn off his other brothers before they all begin to attack. Alex runs to the basement and shuts the remaining HA-Brothers off, only to find out that HA-5 somehow turned himself back on and escaped!

Battle with HA-5
Back in the house, HA-5 chases and attacks Dr. Blackman. Susan grabs a fire extinguisher to knock him back (all the while changing his radio stations, causing him to play different music). Alex joins in and knocks HA-5 to the ground, then punches him into the wall, breaking him (and causing him to play taps).

Blackman and Alex, 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 Blackman's garbage-consuming bot.

Battle with HA-6
HA-6 arrives, having chased Blackman and Alex to the convention center, and viciously attacks Alex. While Alex wrestles with him, HA-6 vents out his vitriolic jealousy, contemptuously calling Alex "mommy's little favourite". They begin to "sword fight" (with pipes) until Alex defeats him.

Meanwhile, Susan fiddles with some left-over electronics on order to create a device to stop the attacking HA-Brothers before it is too late.

Battle with HA-7
HA-7 then appears and forces Susan up against a wall, threatening to destroy her. But because of his lack of confidence and self-esteem, he just gives up and self-destructs without even trying to do any harm to his creator. HA-7 then whines sadly that he cannot even self-destruct properly (as his head is still intact).

Alex becomes anxious, wondering if they can figure out the problem before HA-8 shows up, since HA-8 is stronger than him. This leads Alex to question why, to which Dr. Blackman replies that she had to take out some of HA-8's strength to leave room for HA-9's teenage personality and sense of humor.

Battle with HA-8
Unfortunately, HA-8 arrives soon after, threatening to destroy Susan. Alex fights his tougher brother, but HA-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 Susan'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 HA-8 is finally defeated by Alex, Dr. Locus uses the device again, zapping Alex with it and forcing him to attack his mother.

Battle with HA-9
Alex tries to stop himself, but to no avail. Dr. Locus, determined to destroy Susan, laughs evilly and uses his remote to force Alex to fire lasers and fling sawblades at his mother. Dr. Blackman dashes about frantically, just barely avoiding Alex’s uncontrollable attacks. Then, seeing an opportunity to save herself and Alex, Susan quickly jumps in front of Dr. Locus and ducks just as Alex fires another sawblade, which destroys the remote control device. Unfortunately, it seems as if this does not release Alex from the evil invention’s control, and he extends his arms and grabs Susan in a stranglehold. It looks as if Alex is about to finish off Susan, but then he suddenly hugs his mother lovingly and smiles. Since the remote was destroyed by Susan’s smart and fast thinking, Alex was in fact freed from its control and had been pretending to attack his 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 Susan's trash eliminator.

Back at home, Dr. Blackman and Alex repair the HA-Brothers, who are also back to normal and happy again. But Susan's tiger suddenly appears and swallow her whole, and Susan asks (from inside the tiger) if Alex forgot to feed him...

Trivia

 * This is the very last segment aired on television before the series' cancellation.
 * At the end, HA-5 doesn't appear in the lab like his brothers (unless he 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?"