Not only does the rivalry escalate between Abby and the popular Paige, but a new villain named Insectiva uses pheromones to control giant termites that invade the city.
A bitter sewer worker named Slim merges with a slime mold and turns into a monster who attempts to smother the surface dwellers in slime.
A villain has been replacing ordinary ketchup with a substance that makes everyone fart, and collecting the resulting epidemic of gas to fuel his giant robot dinosaur.
Sloppy Joe, the world's grimiest villain attempts to capture all of the world's smelliest odors, in hopes to unleash a giant stink bomb upon the city.
A former beauty queen invents a weapon that allows her to emulate the Scab Fairy (like the Tooth Fairy) and steal people's scabs so that she can inflict them on others.
Criminals are using an infrasound ray gun that disrupts people's bowels so that they have to go to the toilet.
Insectiva creates a strain of head lice with mental powers that cause the kids at Ringworm High to obey her commands.
Fishy garbage is being stolen from all over the city, and the culprits turn out to be giant mutant hagfish.
An athlete's popular new brand of running shoes creates an epidemic of foot fungus.
A giant Owl terrorizes the people of town and especially its pigeons.
Sloppy Joe sabotages the city's water supply, causing everyone to start vomiting.
When Ty and Lab Rat design and build an experimental new vehicle that can move like an insect, super-villain Insectiva takes this as a challenge and goads Ty into a race.
A new boy in school causes organic materials to rot merely by touching them. Can Ty and Abby cure him?
While Ty engages in the annual Battle Robot tournament, Abby is reduced to cellular proportions by Lab Rat's shrinking ray so that she can battle Lance Boil through the hostile territory of Ty's bloodstream.
Super-villains Instectiva, Lance Boil and Sloppy Joe try to take over the city by infecting the Grossology team with a combination of internal parasites, halitosis and acne.
Deactivating a dangerous device created by Lance Boil causes Abby to be exposed to a ray that makes her age at an incredibly accelerated rate. The Grossology team has to find Boil and figure out how to reverse the process before it's too late.
Engaged in a science project competition with another student, Ty uses an unstable mutagen that produces super-evolving fruit flies that can't be stopped.
Stuck at school with Paige after missing the bus for a camping trip, Ty and Abby discover that a mad proctologist is using the nearly empty school to grow a giant intestine. But to what purpose?
When people start showing up with bite marks on their necks, Ty and Abby can't help but wonder if maybe vampires aren't a myth after all. But when they dig a little deeper, they discover that it's another kind of blood sucker that's causing trouble - leeches! Worse, these hungry invertebrates are led by 869, a giant mutated talking leech that's had enough of his kind being trapped in hospitals under harsh florescent lights. He only has one goal: freedom for leechkind!
Fartor returns with a scheme to turn the entire planet into a gassy giant! But for a plan this big he needs a new assistant - Ty.
Fartor and his new apprentice, Far-Ty join forces to drill into the planet core and turn the earth into one big gas planet. Will everyone on Earth be forced to breathe noxious gas and join Fartor’s army of the fart-breathers or will Abby with Labrat's help be able to save her Brother and the planet from a lifetime of stink!
Kid Rot returns and his powers are out of control.. The forest is rotting and Kid Rot is behind the destruction! Will Abby and Ty stop his rotting tide of evil before he destroys the planet?
A new super-villain, Darko Crevasse, uses an army of nighttime creatures to plunge the city into darkness.
Filthy villain Sloppy Joe returns with his new creation, a booger monster made entirely of snot, which is sucking up everyone's mucus.
When Abby is kidnapped and imprisoned in a greenhouse full of man-eating plants, her only hope of rescue lies with her enemy Insectiva.
Abby and Ty are invited to be contestants on a TV game show similar to Fear Factor, where their ability to withstand grossness is a big asset. The only problem is that it's actually a trap arranged by their arch enemy Lance Boil.
Ty and Abby must stop a feud between Insectiva and her spider loving twin sister, Arachnidia, who are battling each other in the city with giant bugs and giant spiders.
Alligators are popping up in everyone's toilets. Ty and Abby believe that the culprit is a man named T.P. Skinner, who is selling special toilets that get rid of alligators, and Ty and Abby suspect that he put the alligators in the sewers so he can sell his product. What the team doesn't know is that the alligators are a decoy for a much bigger plan made by their old arch-enemy, Lance Boil.
Lance Boil returns, creating a serious case of vertigo for Abby by planting a tiny mind-control device in her inner ear.
Sloppy Joe has supposedly renounced evil and created his own line of fast food restaurants. But then Ty and Abby find out that Joe is collecting all of the trash from his customers and storing it in the old abandoned mine as his own personal collection. Now it's up to Ty and Abby to stop the trash from overflowing and covering the entire town with garbage.
An ex-hair stylist who goes by the name of Frederick Follicle tries to get revenge on the people who rejected his styles by creating a device that will make the entire world bald. Meanwhile, Abby joins Paige and her friends and lets all the popularity go right to her head.
Sloppy Joe plans to make everyone smell like him by creating his own brand of deodorant which makes everyone stink.
Roger Pinkeye, a student at Ty and Abby's school, tries to create a mold monster from the mold found on smelly cheese and it's up to Ty and Abby to stop him without giving out their secret identities.
Lance Boil creates a blaster that causes a person to have bad reactions to the thing they're allergic to. Meanwhile, Lab Rat starts thinking that he might be allergic to Hermies and is afraid that he'll have to leave the lab. Also, Ty tries to impress Naomi by acting like a tough guy.
When everyone at their school gets infected with bad acne, Ty and Abby suspect Lance Boil is behind the whole thing. The only problem is that Lance is in jail. When the acne problem becomes worse, the team has no choice but to ask Lance for help in catching the real crook.
Lab Rat accidentally uses a ray that causes two dust mites to grow. To make matters worse, when he tries to shrink the mites back to normal, he accidentally shrinks Paige instead. Now, Lab Rat must find a way to make everything normal again without Ty and Abby finding out.
Ty and Abby must stop an army of giant dung beetles, that are being controlled by both Insectiva and Sloppy Joe, from rolling huge balls of dung in the city.
Insectiva has created her own spa where all of the treatments are bug based. Ty and Abby's mom is impressed by Insectiva's treatments and the two become good friends. That is, until Insectiva finds out about the powerful bug spray that the kids' mom is working on and she decides to get rid of the spray and it's creator.
A former opera star wants to get revenge on the people who shamed him by attacking places with his powerful burps.
A candy maker by the name of Gary Gumdrop becomes famous when every kid in town wants some of his candy. But then Ty and Abby find out that the candy is coated with bacteria that is giving everyone bad breath and they must stop Gary from giving it to every kid in the city.
Weird balls of light are popping up everywhere in the local swamp. Some people think that it's aliens, but then Ty and Abby find out that it's just swamp gas so they think there's no harm. That is until the gas starts attacking the town.
Ty and his dad go out on a fishing trip in hopes of catching a whopper. But the trip is soon ruined when the campground they're staying at is attacked by giant mutated worms. Now Ty must use his Grossology skills to find out what's going on without his dad finding out.
Ty and Abby talk about the time they first became Grossologists while trying to stop Lance Boil from flooding the entire city with pus.
Roger Pinkeye has kidnapped Lance Boil and is forcing him to tell him everything he knows about the grossologists. It's now up to Ty and Abby to find Lance before he tells Roger all their secrets.
An army of rats is attacking the city and Ty is shocked to find out that the one controlling them is Abby. What he doesn't know is that the Abby he saw was an evil clone created by Lance Boil and his new sidekick, Roger Pinkeye, who is trying to get Abby fired as a Grossologist so he can become one.
Lance Boil and his evil Abby clone are about to take over the Bearu of Grossology and it seems the only one who can stop them is the one who Lance betrayed; Roger Pinkeye.
T.P. Skinner has created a new pet called a slitherbuddy, which is a small creature created by mixing the DNA of different reptiles. Almost everyone in town wants a slitherbuddy. That is, until they shed their skin and turn into giant, savage monsters.
Frederick Follicle returns, but this time he's not just controlling his own hair, he's making the entire town's grow.
The Grossologists go off into outer space to stop Fartor, who has landed on a planet which is covered with fart gas and is planning on sending it to Earth.
Darko Crevasse returns with a dark plot to ruin Halloween via an army of zombie roadkill animals.
Someone's out to ruin Valentine's Day! And it's none other than the love-scorned Insectiva and Sloppy Joe. Now itls up to Ty and Abby to save the day . . . but when they canlt quite catch them, the Grossologists are forced to try a slightly different tact. Insectiva and Sloppy sitting in a tree, k-i-s-s-i-n-g, first comes love . . .
It's another Christmas season, and Abby can't seem to rustle up any Christmas cheer. Not helping is the fact that Sloppy Joe is playing the local Santa this year! But the Grossologists discover something even more sinister when they catch Lance Boil using Joe as a dupe to send rotten fruitcakes to every house in town! It's up to Chef Ty to save the day when Boil's fruitcakes ruin everybody's Christmas dinner.
