Right before Ren is about to enjoy his new "Corn" magazines, he find out that Stimpy is starting his journey into adolescence, complete with all of its trials and tribulations which at first Ren is fine with (since he knows that it's just the journey to adolescence), but starts to get irritated and the last straw is when Stimpy steals his "Corn" magazines.
One evening, Ren and Stimpy receive their mail, which Ren gets. Shuffling through a bunch of letters to Stimpy (possibly referencing Stimpy's Fan Club) he finds his long awaited, new issue of "Husk" a "corn" magazine ("for the adult corn lover"). Eager to enjoy his new reading material in private, he heads to the bathroom, to find Stimpy is hogging it. Beating on the door, Ren demands to bave his turn, but he hears Stimpy, who is screaming in pain as he grows zits all over his face while watching in horror in the mirror, breaks a glass in panic. Ren kicks the door open, to reveal Stimpy, who turns to Ren, to reveal his pimpled face. A shocked Ren soon becomes proud of Stimpy, telling him that he is going through "cat puberty" and is maturing into a man. He adds that this is a blessed, special time in Stimpy's life, through does not hide his selfish nature, saying that once Stimpy becomes an adult, he will be forced to care for Ren in his elderly years by waiting on his every whim for as long as his own. Ren celebrates Stimpy's maturity by fetching him his "Hoek Family Grooming Kit" that contains items such as a jar of leeches, a human ear, and pliers, and has been passed down for generations. Stimpy takes the pliers and uses it by Ren's instructions to pop one of his pimples. He does so, exploding it all over Ren in the process.
The next morning, Ren (with a black eye after getting "shot" in it by pus from the pimple) reads a book about cat puberty to Stimpy, who is cooking breakfast, mentioning his voice will change, he'll get clumsy as Stimpy's voice cracks and he trips and breaks things. Stimpy has prepared a bowl of mush for Ren,, yet, his baby teeth had fallen out while he cooked, falling into the food. Ren compliments Stimpy on his soon to be manhood again (though again, only because he is thinking Stimpy will be his caretaker) Finding Stimpy's teeth in his food, an annoyed Ren brings it to Stimpy's attention, but as his hormones begin the rage, this begins making him more emotionally sensitive. Stimpy says he feels like Ren is yelling at him, and nearly in tears reassures them that he's "a good boy". Ren accuses Stimpy of being too sensitive. All of a sudden, another growth spurt hits Stimpy. His spine forcefully, and very painfully, grows new vertebrae to force him taller; his adult teeth come in to replace his baby teeth. Ren tells Stimpy that it's another growth spurt and tries to reassure his friend, who he is now acting more like a father figure to him now, that he'll be okay; however, Stimpy looks at his "disfigured " body and has a emotional breakdown, saying that he looks stupid and he doesn't want to grow up, causing the feline to go on a rampaging tantrum, smashing furniture, the house, and running through it screaming and crying hysterically as Ren watches in confusion, horror and sadness.
The following morning, Stimpy wakes up with a "bulge" under his covers, revealed to be a chest hair, which he deems his "first *grownup* possession" referencing his catchphrase about his litterbox. Running to the bathroom to presumably gawk at it, he cuts Ren off, who again get angry. Stimpy combats this by giving Ren a bucket to do his business in. To make matters worse, Stimpy's behavior continues to get worse as he begins to act more like a stereotypical teenager, to Ren's increasing frustration and annoyance. Stimpy has hooked up the telephone to a switchboard to communicate, chat and gossip with his various friends and make crank calls, adding insult to injury, he begins to say disrespectful insults and say things about Ren behind his back in the fashion of a spoiled teenager back talking about their parents rudely, further pushing a increasingly agitated Ren closer off the deep end. He reads a book on child discipline while trying to convince himself Stimpy will grow out of this "phase". Stimpy molts his skin like a reptile, leaving it as a mess all over their home and forcing Ren to clean it all up with no help. Stimpy approaches Ren and seemingly, having a change of heart, asks Ren if he'd like to go out. Ren, believing Stimpy was mellowing back out, agreed. However, Stimpy says bluntly that he means that he just wants Ren to go away so he can have his friends over as he finds Ren embarrassing. Hitting a string with Ren.
Stimpy invites his friends over and Ren decides to try to change his approach to be kinder to him. He brings sodas to Stimpy's room, which he has written "No Chi Hoa Huas" (Chihuahuas; meaning Ren in particular) on his bedroom door (Ren misreads it as "chai hah hahs", and plays it off as teenage slang) which Ren knocks on. A puff of inconspicuous smoke floats out of his room and bubbling water is heard in the foreground as the door is answered by an annoyed Stimpy. Ren offers them soda, and Stimpy slams the door in his face. A nervous Ren knocks again and now wants to meet Stimpy's friends and forces his way in. Stimpy introduces his two "friends" to Ren (two large overdeveloped to the point of nearly being grown men) are crossing off numbers of years on their back from the class yearbook, with ink guns, thus giving themselves tattoos. Ren finally has had enough and puts his foot down and labels Stimpy's "friends" as nothing more than "delinquents", accusing them of corrupting his friend/son. He kicks the two out as one asks Ren if will tell their parents, which only makes Ren madder. Ren then tells Stimpy, fed up with his behavior, that he cannot leave his room until he's a adult, and that he is grounded forever, washing his mouth out with soap.
Later that night, Ren watches home movies on a film projector, of he and Stimpy playing football when he was a kitten. Ren sniffles between bittersweet tears as he reminisces Stimpy's "youth". Meanwhile, Stimpy has snuck out of his room with the plan to check out Ren's Husk Corn Magazines. He sneaks past a gloomy, nostalgic Ren unnoticed to the Chihuahuas bedroom, where he goes into his underwear drawer and finds the motherload-- Ren's entire corn stash. Stimpy runs off with the literature to another room, where he opens a centerfold in one of the magazines; an ear of corn on a stalk, which puts hair on his back. Stimpy goes into manic laughter and rips out the pages, licks them and proceeds to attach them to his body.
Ren begins to feel guilty for punishing Stimpy so badly, and vows to "make it up to him next year" when he notices his "security system", a hair taped on both ends on his dresser drawer has been broken, he begins to mad, opening the drawer to find all his magazines gone. Furious, he exclaims that Stimpy has "gone through another man's drawers", and begins to come after him, saying that he should've done this back in "scene 36". Grabbing a mounted sailfish off it's plaque, and carrying it like a bat, he finds Stimpy in the dark room he escaped to; revealing he used all of the pages of Ren's corn to cover his body and glued himself inside to the ceiling with spit. Ren is slightly touched by the gross scene, describing it as the "pupa stage" from which he will emerge as an adult. However, Ren's feelings do not last long as he whacks Stimpy's pupa violently with pure anger, in the style of a pinata, feeling no sympathy for him anymore.
Suddenly, Stimpy's pupa cracks, and out wiggles a much more muscular and handsome Stimpy with a full head of hair, having grown into a superhero complete with costume and cape. Ren is proud, congratulating his pal on having "grown up". Though, Ren begins to explain that Stimpy must take care of his "old man" and be in his debt. As Ren tells Stimpy how he must now bathe him, feed him, and "wipe the drool from my chin", Stimpy uses his newfound x-ray vision superpower on Ren, looking at his muscles, organs, and bones. After seeing that, Stimpy decides that the "world needs him" apologetically declining Ren's offer of Stimpy to care for him forever. He tells Ren "Thanks for the grub, old man! I'll call you when I need money!" Stimpy bashes through the wall (after tearing the crotch area of his "costume", actually his fur, revealing his underwear) and flies off into the sky. Ren tries to stop him to no avail. Stimpy tells Ren that he will write if he ever learns how. Ren weeps, watching Stimpy fly off, and turns to the audience, remarking that the hardest thing a parent goes through is to see their child move away and start their lives as adults, and all we can do is hope that we raised them right. Ren forlornly waves goodbye to Stimpy, who continues flying as a small dot through the sky into space towards the sun; which, in his stupidity, he flies directly into, thus obliterating to death instantly, not only destroying his bright future, but also making all of Ren's efforts and pain meaningless and he will die alone as the episode irises out on Stimpy vaporizing into smoke on the sun.
- The episode's title is a parody of: "I Was A Teenage Werewolf"
- The two of Stimpy's friends are overgrown versions of Archie and Jughead from the Archie Comics.
- Corn Magazine is an obvious parody of Porn Magazine.
- At one point, Stimpy has no ears. When Stimpy covers his eyes, his ears reappear.