At the beginning of the episode, Randy and Howard are discussing the Ninja Sword. Specifically, Howard is convinced the Ninja Sword can't cut through a bulldozer. Randy argues with him about this for a while, even rattling off a short list of many things the Ninja Sword has already sliced cleanly through, although Howard remains unconvinced ("Can it cut through a Bulldozer? Because I'm pretty sure you didn't say 'Bulldozer'"). Randy then realizes where this is headed and stops the argument immediately, declaring that he is NOT going to be tricked into cutting up a Bulldozer.
Scene Transition to Ninja standing atop a Bulldozer asking Howard how he'd like it sliced (Howard opts for "Ninja's Choice"). Unfortunately, Howard ends up being right, as the Ninja Sword simply bounces off of the Bulldozer's metal chassis. In addition, much to Randy's horror, the Ninja Sword immediately shatters.
After failing a (very poor) attempt to repair the sword himself, Randy consults the NinjaNomicon after it buzzes at him angrily. The NinjaNomicon reveals to Randy that "In the realm of the Ninja, a swordsmith crafts blades in a cauldron of fire.", apparently deciding not to lecture Randy much this time (although it gives him a good, hard smack on the way out).
Later at school, Randy is walking down the hall with Howard, attempting to decipher the cryptic instructions, having deduced that the school is obviously "The Realm of the Ninja." Eventually they pass by the Metal Shop class and notice the sign on the door bearing the instructor's name, Mr. S. Ward Smith. Noticing the obvious wordplay at work, Randy deduces Mr. Smith must be the swordsmith the NinjaNomicon was talking about, and enters the metal shop class to speak with him, though not before an angry Brent barges past them.
Moments ago Brent was attempting to craft a pair of corn-cob holders, apparently at the behest of Mr. Smith. We discover he is Mr. Smith's apprentice and this is some sort of test for him to learn the fine art of metalwork. His corn holders fail once more, and Mr. Smith tosses them into an obscenely large pile of similar rejects. Frustrated with this seemingly unrelated and silly task, Brent angrily storms away refusing to continue the task any further, passing by Randy and Howard as they are about to enter.
Now Randy and Howard enter the room, although Mr. Smith doesn't appear to be there at the moment. Randy calls out that he is looking for an actual swordsmith, when Mr. Smith suddenly appears from behind a table and demands to know why the two students are poking around his Metal Shop after class hours. After noticing that Mr. Smith is blind, Randy decides to announce himself as The Ninja, only to find that the old metalshop teacher had known all along, claiming Randy reeked of Smoke Bombs.
Just a few seconds later, Brent is outside the door to the classroom, having calmed down and deciding he wants to apologize for his outburst previously. When he opens the door, however, he finds Mr. Smith seeming to be impressed with some dents Howard had put into a metal plate ("Hey, look! I made some dents!"). This fuels Brent with rage when he interprets this situation as Mr. Smith's having chosen Howard as a replacement apprentice, and he once again storms off. Afterwards, we see the truth of the situation. Mr. Smith was simply pretending to be impressed, immediately afterward explaining to Howard that they are only dents, which a donkey could also do ("That's ridiculous! Donkeys can't hold hammers..."). However, it is too late for Brent, as he's already made his way into the boiler room to beat his frustrations on a metal pipe, which catches the attention of The Sorcerer. He takes advantage of Brent's fury and rejection right away, immediately possessing the young apprentice with his powerful stank. In this new monster form, Brent spends some time in the boiler room crafting a suit of powerful metal armor to wear.
Back in the Metal Shop classroom, Randy interrupts the argument between Howard and Mr. Smith to bring focus back to his current predicament, trying to vocalize his issue although unable to admit it out loud. Mr. Smith seems to simply infer from Randy's reluctance that he's broken his sword, which Randy then admits to, although wondering how he figured it out. Mr. Smith then guides Randy into his secret forge, which is home to thousands of swords, and his Sacred Fire Pit, revealing that he's crafted swords for the Ninja of Norrisville his whole life. Randy is excited for his replacement sword, as Mr. Smith brings down a very important looking box, only to present Randy with a clown-balloon tied into the rough shape of a sword. He tells Randy that until he can prove he can be responsible with his weapons, this balloon will be his new sword. Randy is disappointed to say the least, and takes to the challenge with a cocky attitude at first, proclaiming "this is baby stuff", although immediately popping the balloon on a nearby sword at that very instant.
Over the course of the day, Randy continues to lose balloon-swords in various ways, Mr. Smith becoming slightly more frustrated with each loss ("I'm beginning to think you don't even WANT a sword!"). Eventually Randy becomes more and more protective of each balloon, getting a little better at the task with each loss. At around lunchtime, Randy is reassuring his new balloon-sword that he won't let anything happen to it, both Howard and Mr. Smith nearby regarding him with pity.
It is at this point that Monster-Brent bursts out of a hole in the ground in the middle of the lunchroom and snatches Howard, before disappearing back down said hole. Randy prepares to give chase, although not before taking his balloon-sword with him, not wanting to let it out of his sight.
Monster-Brent rampages down the hall with Howard in tow, eventually bringing him back to Mr. Smith's class and proclaiming "ME APPRENTICE. HIM NOT APPRENTICE!!!" ("How come you have so much trouble with grammar, but you can say 'apprentice'!?"). The Ninja smokebombs onto the scene, and begins battle with Monster-Brent (although not before a brief and comedic exchange between Howard and Randy).
In the Ninja's attempts to battle Monster-Brent, he finds all his current weapons harmless, bouncing off of Monster-Brent's powerful samurai armor and causing the monster little more than a bit of an annoyance. Randy ducks behind Mr. Smith's desk and bemoans his lack of a sword, when Mr. Smith's words echo in his head "Until you can prove to me you can be responsible for your weapons, THIS is YOUR sword!". Randy interprets this as a Ninjanomicon-style lesson-of-the-day and determines that perhaps the balloon has some kind of magical Ninja power that can help him win the battle. He then immediately re-engages Monster-Brett, bapping him repeatedly with the balloon-sword, although once again doing little more than annoying him.
It is at this point Mr. Smith emerges from his secret forge and demands to know why the Ninja thinks he's doing. Randy proclaims he understands the true meaning of Mr. Smith's message, and that he's going to take his "sword" into battle like a true ninja. Mr. Smith tries to explain he's wrong ("WHAT!? That's not a SWORD... it's a METAPHOR! Are you TRYIN'A get yourself killed!?"), although a bit too late as the balloon is popped in a brief exchange and Randy is thrown by a powerful punch.
The Ninja lands on Mr. Smith's desk and bemoans the loss of his balloon sword, only to find that Mr. Smith has finally crafted his ACTUAL new sword, having determined the Ninja worthy of his new weapon ("Now THAT sword would cut through a bulldozer!"). With his new sword, Ninja defeats Monster-Brent, slashing his stanked smithing-hammer to return Brent to normal.
In the final scenes, Randy and Howard reflect on the day's lesson of responsibility... especially because Sais are much cooler to goof around with.
- Mr. Smith tells Randy the Ninja Sword can cut through anything, "except stupid", and also that Ninja Tools are only for Ninja Business. This seems to imply that the sword broke NOT because it was incapable of cutting the bulldozer, but because the bulldozer was unrelated to ninja business (in other words, the ninja sword would have probably been able to slice the bulldozer if Randy had actually needed it to).
- In this episode, Randy acts like he only has one sword, but in several previous episodes (like "Attack of the Killer Potatoes" and "30 Seconds to Math"), it's shown that he has two dual swords.
- Randy gains a new sword in this episode, which appears in every episode afterwards (except episodes that were likely aired out of order, like "Ninja Camp").
- S. Ward Smith, a swordsmith, is the first person known to work for the Norrisville Ninja, making and replacing broken swords.
- Mr. Smith and his metal shop were mentioned previously in "Monster Drill".
- Although recognizing the Ninja because he reeks of smoke bombs, S. Ward Smith is blind, so he probably doesn't know the Ninja's true identity.
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