As the Ninja, Randy defeats another of McFist's robots — this time by removing its power source. Randy brags to Howard about his victory, declaring that he's become too skilled to beat, but Howard counters that the robot was simply too easily defeated, and suggests that Randy has become overly predictable — Howard could easily manipulate Randy into anything if he put his mind to it. To prove his point, Howard manipulates Randy into giving him the only remaining portion of fries for lunch, declaring to a horrified Randy that he is the "mastermind." Throughout the day, Randy tries to disprove Howard's claim but fails miserably at every turn, leaving him to finish Howard's homework instead and suffer various pranks. Howard, pleased at these developments, continues to scheme up more embarrassing pranks.
Meanwhile, Evil Julian has not been able to locate the Sorcerer's Power Ball, and coerces Julian into helping. Julian, imprisoned in the Shadow World, tries searching the bag that originally contained the ball for the umpteenth time; this time, Evil Julian notices Randy's name sewn to the bottom of the bag, and decides to go after Randy.
While Howard continues setting up his latest prank, Randy hides in the toilet to consult the NinjaNomicon, having become crazy at being outpredicted by Howard at every turn. The NinjaNomicon tells him that
|“||The unexpected is never expected||”|
which only serves to confuse Randy. Randy guesses that the only way to counter Howard is to do something unexpected. At the same time, Evil Julian confronts Howard over Randy's whereabouts, and goes to find Randy in the toilet just as the latter is leaving. Randy, surprised, learns from Evil Julian that Howard had sent "Julian" to him, and grows suspicious.
Outside, Randy triumphantly tells Howard that he's defeated Howard's prank by doing something unexpected: he gave "Julian" the Sorcerer's power ball. Howard blankly tells him that sending Julian wasn't the prank, and Randy realizes he's goofed up. Evil Julian, now supercharged by the Power Ball, proceeds to destroy Randy's dimension. Randy goes Ninja to confront him, thinking it's still regular Julian. Evil Julian declares himself to be Julian's evil counterpart, which Randy doesn't recognize - at this, Evil Julian breaks into a rant about how no one noticed the switch despite the two Julians looking obviously different. Noticing the broken pieces of the robot Randy defeated earlier, Evil Julian assimilates with the parts to assume a stronger form.
Randy barely manages to hold his own against the stronger Julian and is forced to run away, when he notices a trap of plastic wrapped around two trees that Howard had set up. Remembering the NinjaNomicon's wisdom, Randy successfully lures Evil Julian into the trap while avoiding it completely, wrapping Evil Julian in the plastic. Howard is surprised that Randy finally saw through one of his traps. Using a throwing disc, Randy detonates the robotic power core and sends Evil Julian flying, satisfied with his latest victory.
However, Evil Julian soon regains consciousness and now knows who is in possession of the Sorcerer's Power Ball.
- The title is based on the nickname "Master of Disaster," often used of athletes such as boxers or wrestlers who inflict heavy damage on their opponents.
- Evil Julian gets the first Sorcerer's Ball in this episode.
- Footage from "Randy Cunningham's Day Off" is reused in this episode.
- Randy doing a split on two driving cars' mirrors is a reference to a commercial starring Jean-Claude Van Damme in which he performs a split on the side mirrors of two moving trucks.
- This episode reveals that Randy’s real name is "Randall."
- The Titmouse animation studio logo appears as a bird in this episode.
- In this episode, Debbie Kang appears in the cafeteria wearing a dark short dress instead of her normal dark khaki shorts.
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