Small town life above the Arctic Circle snowballs out of control when an enormous, outrageous, and unstoppable Yellow Yeti arrives in town and befriends two 12-year-old kids.
Osmo's arrival gets stranger when he befriends a yellow yeti called Gustav. His amateur monsterologist cousin Rita suspects a monster is afoot, which is against Winterton rules.
Osmo and Rita's first family dinner goes badly, jeopardising Osmo's stay in Winterton. Gustav must save the day in a clever chef disguise, right under Mayor Chrome's nose.
When Osmo has to get a skiing license or be banished, becomes his clueless ski instructor and Rita pits him Mayor Chrome in a downhill race to stay in Winterton.
When monster panic strikes Winterton, Gustav volunteers as a stand-in yeti for Mayor Chrome's monster-preparedness drills, but struggles to be convincingly scary.
When Gustav thinks his Grampapa has been turned into Chrome's new rug, the kids help give him a send-off at Monster Graveyard. But Osmo must first conquer his fears.
When Osmo's inflatable doughnut goes missing with everyone's mail, the trio search for Winterton's Mail Cats, who have gone feral. The Northern Lights offer help, for a sacrifice.
When Ned thinks Osmo needs company, he gets him a cute pet which turns out to be a vicious monster. Osmo and Gustav must get rid of it before it destroys Winterton.
Rita finds proof that her hero, Emma Erton, was the true founder of Winterton, but loses it to Anders and his cronies. Osmo and Gustav must help her fight for it back.
When Osmo and Rita suspect Gustav is going 'full monster', they trap him so they can find a cure, only to get symptoms themselves. Now Gustav must figure out how to cure them.
A lake monster cozies up to Gustav in the belief that he wants to take her out for dinner, with Osmo and Rita as the main course.
When Osmo's eagerness to fit in by celebrating Winterton's founding leads to disaster, he must use his wits as an outsider to save the town with Gustav and Rita's help.
When Gustav plucks a legendary plunger from the town toilet, he thinks he's Winterton's one true plumber, leaving Ned bummed. Osmo and pals must help him get his confidence back.
When Osmo signs Winterton up to host the Winter Games, Chrome is caught unprepared. The trio must rally the town to put on a big show for the demanding Chairman.
When Osmo discovers a monster who looks just like him, he teaches him how to have fun, only for his clone to cause chaos all over town. Now the trio must tame the terrible twin.
When Rita competes with Osmo and Gustav against Anders' crew in a sauna competition, her competitive side emerges. Osmo and Gustav must get her to cool it before she blows her top.
When Spring doesn't come, the townsfolk begin acting strangely. It's up to Gustav to perform various ridiculous deeds before the Northern Lights will bring on Spring.
When Rita takes her mom's secret amulet, the trio experience bad luck and suspect that Lydia may be a monster. They must make amends to break the curse.
When Osmo, Rita, and Gustav get trapped in a gondola, their friendship is tested by panic and paranoia, while Chrome and Ned bicker over how to get them back down to Earth.
The trio's scheme to bring online delivery to Winterton is a huge success, but when they drive Mr. Cavity's shop out of business, they must remind everyone of his old school charm.
When Gustav is mistaken for a giant teddy yeti by Anders' spoiled little sister, Osmo must break him out of their house, even if he has to play friends with Anders.
When Rita's talent for chainsaw ice sculpting goes from scary to awe-inspiring, Osmo and Gustav investigate if it's really her work, while Rita frets over her upcoming exhibition.
It's Osmo's worst nightmare when he gets stuck to Anders with pinesap on a field trip, and both wind up lost on Monster Mountain. The two must get over their rivalry to survive.
When Rita replaces Chrome with Gustav as mayor, it's all good fun until chaos befalls Winterton. The trio must work with Chrome to save the town from an ice-volcano eruption.
When Mayor Chrome forgets his wedding anniversary, Rita and Osmo pull out all the stops to keep her parents together, only for her mom to run off with Gustav instead.
The kids help Gustav dress up for the Ball, only for the yeti to be crowned belle for a whole year. Now they must help him keep up appearances or risk being exposed as a monster.
When Chrome puts Winterton on an all-beet diet, Rita rebels by supplying townsfolk with Monster Fizz Dipper on the sly with Osmo and Gustav's help, causing odd side effects.
When Chrome seizes Osmo's snowboard, he calls up Gustav's monster-burglar pal, Geddin, to help him get it back, only for her to clean out the Mayor's Mansion to Rita's horror.
Osmo and Gustav get jobs as delivery guys to raise funds to celebrate Rita's graduation from Anger Management class, only for Rita to think they ditched her, testing her fury.
Osmo kitten-sits for Katz in a hostage deal for his beloved childhood plushie, but when the kitten goes missing he ends up on wild monster hunt with Gustav and Rita.
After Osmo dodges an awkward talk by accidentally freezing Ned in ice, he must take his place as Winterton's plumber, with Gustav as assistant and Rita translating Ned's blinks.
When Gustav boasts to Osmo and Rita about visiting a patch of forbidden Rainbow Snow atop Monster Mountain, he regrets it when they fall foul of its weird, mind-bending powers.
When Osmo and Rita visit Gustav's family, they're forced to keep his life among humans a secret while dodging Grampapa's appetite. Gustav must come clean to save his friends.
When Osmo, Rita, and Gustav do a good deed for old man Ukko, he tempts them with tales of his fortune, leading them to compete for his favor and risking their friendship.
Osmo and Rita join Gustav to celebrate his ancestors at the Monster Graveyard, only to wake them up by sharing spooky tales. Now they must tell the spookiest tale ever to escape.
When Gustav discovers Future Gustav is alone and friendless, he goes overboard to protect Osmo and Rita, only to lead them into harm's way. Now he must save them from himself.
Rita swaps homes with a monster girl named Emmer for Monsterology research, but when Emmer wants Rita's life in Winterton indefinitely, Rita finds herself becoming truly monstrous.
When Rita rescues a sapling, Osmo and Gustav's fertilizer turns it into a giant monster tree. Rita wants it to stay rooted in Winterton for safety, but it wants to roam free.
When Osmo insults a weasel, he ignites a war between weasel-dom and Winterton. Osmo must find a way to apologise before the critters ruin a beloved Winterton tradition.
When Gustav, Osmo and Rita get locked in the Town Hall with Rufus, paranoia causes all four to suspect each other of being a shapeshifting monster. They must build trust to escape.
When Osmo and Rita ruin Gustav's heirloom monsterdough recipe, he guilts them into a quest up Monster Mountain to recreate the gross dish by using all their senses, at their peril.
When Rita seeks Ukko's guidance to go with her gut instead of her brain, Osmo and Gustav suddenly forget how to have fun without her - putting the trio's friendship on thin ice.
When Rita's mom goes on a secret trip, Osmo and Gustav help Rita find the truth about her monstrous past, only to find a bigger, ancient secret affecting monster and humankind.
When Gustav's monsterbread bursts and makes all of Winterton lose their memory - he, Osmo, Rita and Rufus think they're a royal family. But their random rule leads to revolution.
When Gustav tries to track a beet-stealing Wolverine, he shuffles through all his personas to outsmart it, in vain. Osmo and Rita must encourage him to use his own unique wits.
When Gustav becomes Winterton's Winter Games mascot, he enjoys walking around undisguised, but soon suffers under the townsfolk's ideas about how their mascot should behave.
When Rita gets growing pains, Lydia helps get her worries off her chest with a romp on Monster Mountain, while Chrome tracks them with Gustav and Osmo as his hapless search party.
When Osmo digs through Chrome's rule book, he discovers a hidden rule that could banish him or Chrome from Winterton. Gustav and Rita try to find a loophole to save them both.
Rita tries to give her dad the toy of his boyhood dreams to cheer him up, but gets conned out of her home by Mr. Cavity. Her, Gustav, and Osmo must out-con him to save the day.
When Rita and Osmo discover that Gustav is not allergic to singing, but can sing too, they enter him into the Wintervision Song Contest, only to risk exposing the yeti in public.
Osmo, Rita, and Gustav must convince all monsters that they're immune to the Chromatron's yodels. Getting them to sing along with humans will be key to saving their communities.
