Three young monsters — Ickis, Oblina and Krumm — attends an institute for monsters under a city dump and learn to frighten humans.
Simon the Monster Hunter builds the ultimate monster hunting machine; The Simon-Mobile, in an attempt to capture a real monster. When the monsters get wind of this, they build a machine entirely out of garbage and go head to head battle with Simon. With The Gromble at the helm, the monsters emerge victorious.
Feeling like Ickis and Oblina are not paying him enough attention, Krumm moves out of their dorm room and into the room of two other monsters - Snav and Blib. These two monsters spoil Krumm with attention, which he needs - at first. But soon Krumm realises that being the centre of attention is not all it's cracked up to be.
A case of mistaken identity leaves Ickis thinking six lobsters are actually six monsters. He saves them from being served as dinners and promises to see them safely home.
Oblina loses her lips when they get caught on a construction barricade and ripped off. The lips are found by would-be model Lucy Schmeeler, who glues them on and is proclaimed a sensation by Modelling Agency Owner Dietrich DuChamp.
When Ickis gets stuck in a toilet in Rock Star Suede's house, the monsters' only hope is to disguise Ickis in Suede's coat and hat and try to walk home. The trip home turns into a disaster as the monsters get tossed out of a taxi, cause a massive pileup and are chased back to the dump by TV Reporter, Exposia Vertov, and a horde of screaming teeny boppers, who think the disguised Ickis is Suede.
When Ickis meets a monster with a human face, he not only gains a private tutor, he makes a friend. As a youngster this human-faced monster was the object of such ridicule that he ran away from the dump and has hidden in the human world ever since. Now it is up to Ickis to convince him that the monster world has matured enough to accept this handsome monster as he is.
While getting ready to do a scare at a hypnotist's show, Ickis stares at the hypnotist's watch and inadvertently gets hypnotised along with the hypnotist's intended subject - a loud-mouthed Car Salesman. Oblina and Krumm are mystified that whenever the word "human" is uttered, Ickis begins to act like the Car Salesman.
Through a series of misinterpretations, Krumm is convinced that Oblina has a crush on him. Krumm gets paranoid about what this will do to their friendship and tries desperately to avoid her.
When a group of "cool" girl-monsters shuns the obsessively rule-bound Oblina, she transforms herself into Oblina The Rebel--breaking every rule she can.
When a cocky Ickis takes a break from scaring to eat the grime of a dirty car, he inadvertently ends up in a car wash. Now covered with three coats of wax, the frictionless Ickis must slip and slide his way through an important scare. Luckily for him it's at an Ice skating rink! Ickis out "slips and slides" everyone.
Ickis, Krumm and Oblina get trapped inside a nuclear power plant when they accidentally set off a warning device closing down the entire facility. Seeing the three monsters on a monitor, one of the plant workers mistakes them for three plant employees. A team of highly trained doctors don protective clothing and go inside the facility to bring the "employees" out to safety.
The monsters are overjoyed when the famous Loch Ness Monster pays a visit to The Academy to give a guest lecture. Unfortunately, the rowdy, boisterous Scotsmonster gets on everyone's nerves by relentlessly singing Scottish songs, dancing and re-enacting his famous scares.
Alone in the dump, Ickis dons a cape and pretends to be his favourite comic book hero, "Ultra-Monster". Suddenly, he is accidentally thrown through the air by a bulldozer and inadvertently saves a group of students. It's a bird, it's a plane...it's Ultra Monster! Word gets around the academy that "Ultra-Monster" is real and very cool. When Krumm volunteers to play sidekick, "Stink Boy", a new dynamic duo is born.
A substitute teacher arrives, announcing that The Gromble has "gone away" and that he will be taking over. The substitute lets the students do whatever they want - even garbage fights are allowed!
Shortly McGinty, arch-criminal and master of disguise, escapes from prison and leads the police on a chase that takes him to the dump, where the cops mistake Ickis for McGinty and haul him off to prison.
When Krumm is forced to wear glasses to correct his inexplicably blurry vision, he finds himself the object of mocking on the part of the other students. Krumm tries to go without his glasses, but he and all the students learn their value when a bespectacled Krumm saves a group of monsters after a scare goes wrong.
The Gromble assigns Ickis to be "pair-scare" partners with the dreaded, unpopular Zimbo. Ickis and Zimbo are miserable with the match and instantly start fighting.
Ickis discovers as easy way out of getting his homework done. By tapping into humans' phobias, he is able to bring scare after scare to class with little or no effort. That is, until The Gromble sends him to a phobic-free human to scare.
The Academy shuts down when a human spy is discovered inside. From Ickis' hiding place, he realises he has dropped a drawing of The Gromble in the hallway. The spy picks it up and accidentally drops his own secret document. Ickis, Krumm and Oblina use the paper to track down spy headquarters and arrange for a transfer of the documents.
The Gromble is in love with the Library Monster, and he's not as strict as he used to be. Ickis is thrilled and wants to make sure that The Gromble stays in love, but The Gromble is unsure how to behave with a lady -it's been so long- so he asks Oblina for helpful hints.
Ickis is perpetually late for class, so The Gromble hangs a big clock around his neck to remind him to be on time. When Ickis rewinds the hands on the clock, he discovers that he can turn back time.
The Gromble is sick and Simpah, the horrible Cafeteria Monster, has been put in charge of the students. When she threatens to make them eat human food, Ickis, Krumm and Oblina beg The Gromble to come back. The Gromble says the only thing that will cure him is Gromble Soup, but you need special ingredients....the crown of a king, the head of a dragon and the tail of an ogre. Ickis, Krumm and Oblina each set out to obtain one of the ingredients.
Simon the Monster Hunter hires three of the greatest hunters in the world to help him capture Ickis and prove to the world that monsters do exist. When Ickis proves to be more difficult to catch than the hunters had anticipated, the hunters' pride gets the best of them. They turn away Simon's money and set their sights on doing more than just "capturing" Ickis.
A hungry parasite named Sal invades Oblina's stomach, causing her to eat everything in sight. Ickis and Krumm shrink down to Sal's size, enter Oblina's body and battle it out with him inside Oblina's expanding stomach.
The Academy is gearing up for the Scaring Olympics. The Gromble wants desperately to win the competition and is pushing his students to do their best. Unfortunately, Krumm has swallowed an Indian feather that is tickling him on the inside.
Ickis, Krumm and Oblina get trapped in a garbage compactor and the only thing they can do is bicker. As their impending doom approaches, they remember their first days at The Academy.