2. The Slim Slime Man

A bitter sewer worker merges with a slime mold and turns into a monster who attempts to smother the surface dwellers in slime. Meanwhile, Ty tries to get more people to eat at the cafeteria.

3. Fartzilla

The villain, Fartor wreaks havoc and seeks revenge on his cruel brother by causing a fart epidemic in order to fuel a giant robot called Fartzilla.

4. The Perfect Stink

Sloppy Joe, the world's dirtiest bad-guy, takes all the worst smells in the world and makes a giant stink bomb. Meanwhile Ty asks Naomi out on a date.

5. The Scab Fairy

A former beauty queen, calling herself the "Scab Fairy", invents a weapon that allows her to steal people's scabs so that she can inflict them on others.

6. When Ya Gotta Go

Lance Boil builds an infrasound ray gun that causes instant diarrhea, thereby severely hindering any police investigation.

7. Club Parasites

Insectiva has created a strain of giant mind-controlling head lice that grow on all the kids' heads at Ringworm High, converting them to zombies.

8. Go Fish

Mutant hagfish attack the town. Ty and Abby follow their slimy trail of destruction. Meanwhile Ty and Abby get a pet kitten named Hairball.

9. It's Gotta Be the Shoes

A crazed basketball player creates a plague-like Athlete's Foot epidemic using his new brand of popular running shoes.

10. Owl Most Foul

A giant Owl terrorizes the people of town and especially its pigeons. Meanwhile, Lab Rat refuses to come out of the Gag Lab because of his fear of the outside world.

11. Yack Attack

An attack on the city's water system makes people sick.

12. The Greatest Race Ever Crawled

Ty and Lab Rat design a vehicle that crawls and leaps like an insect, and then are challenged to a race by Insectiva.

13. Kid Rot

A boy causes organic things to rot just by touching them, so Abby and Ty try to cure him.

14. The Insider

Lance Boil shrinks himself and tricks Ty into drinking him so he can tinker with Ty's brain once inside his body.

15. All Together Now

Instectiva, Lance Boil and Sloppy Joe inflict the members of the Bureau of Grossology with parasites, halitosis and acne in an effort to take over the city.

16. Oldie but a Goodie

While defusing a device Lance Boil planted in town, Abby gets hit by a ray that instantly starts aging her at 6000 times the normal rate.

17. Survival of the Grossest

Competing in the school Science Fair, Ty's main rival is Patrick and his cool robot. Deciding to jazz up his fruit-fly project with a little mutagenic kickstart, things go wrong almost immediately.

18. School's Grossed Out for Summer

A mad proctologist, Dr. Colon, breeds a giant intestine that he intends to snake around the world, unless Ty, Abby, Paige and Naomi can stop him.

19. Vein Drain

When people start showing up with bite marks on their necks, Ty and Abby suspect vampires. But when they dig a little deeper, they discover that it's another kind of bloodsucker that's causing trouble – leeches! Worse, Abby is deathly afraid of these hungry invertebrates.

20. Silent But Deadly, Part 1

Gassy super villain Fartor returns with a scheme to fart-up the entire planet! But with a plan this big he needs help, and he's got his sights set on Ty.

21. Silent But Deadly, Part 2

Fartor and his new apprentice, Far-Ty join forces to drill into the planet core and turn the earth into one big gas planet. It is up to Abby to stop the gassy bad-guy and re-convert Ty back to an oxygen-breathing Grossologist.

22. The King of Rottingham Forest

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?

23. Lights Out

A new nocturnal villain, Darko Crevasse, plunges the city into darkness with the help of his army of creatures of the night. Ty scrambles to shed some light on the problem before it's lights out for everyone.

24. Frankenbooger

Sloppy Joe creates a friend out of stolen boogers.

25. A New Leaf

Abby is kidnapped and placed in a greenhouse filled with man-eating plants.

26. Heave It or Leave It

Abby and Ty are jazzed to be contestants on the hottest game show on the planet where their gross skills and iron stomachs could make them stars. Only trouble is, The Director forbids them to go on. However they disobey him and go on anyway only to discover the show is an elaborate trap set up by Lance Boil.