One of the main characters, a tomboyish girl who unravels mysteries so disgusting that no adult will touch them. She is very intelligent and loves everything gross and slimy. She likes to test her limits to see if there is something that can make even her, the Queen of Squeam, turn green.
- Action Girl: She frequently brawls with villains during missions.
- Action Hero
- Badass Adorable:
- Enemy Mine: She once teamed up with Insectiva to get rid of a carnivorous plant-themed villain, since said villain threatened both of them.
- Expy: Often compared to Kim Possible, if she had darker hair and was into gross things.
- Fatal Attractor: Every (named) male she's expressed an attraction towards on the show has turned out to be a supervillain.
- Genius Bruiser: She can fight with both her wits and knowledge and brute force; she's both street-smart and book-smart.
- The Lad-ette: Her tomboyish-ness and love of gross things helps her in her job though.
- The Leader: Out of the two siblings, she most likely to take the lead.
- Little Miss Badass: Perfectly capable of holding her own against even the most powerful of villains and is a teenager.
- Plucky Girl: Even when it seems like the end, she never gives up.
- Rapunzel Hair: Abby's hair is about as long as her body.
- Tomboy: This is a given since she's a grossologist. Her interests include things that involve being active and has no problem whatsoever with dealing with gross situations.
- Teen Genius: Knows a lot about biology and anatomy.
- Tomboyish Ponytail: A definite tomboy who wears her hair in a long ponytail.
- Why Did It Have to Be Snakes?: She's very afraid of leeches, as shown in the episode "Vein Drain."
Abby's younger brother and the other main character. He is very intelligent, possessing a cool, active and analytical personality that takes everything in. He sees himself as a scientist and takes his job as a Grossologist very seriously, and his goal is to be remembered among the very best within the scientific community.
- Action Hero: Kicks just as much villain ass as his sister does.
- Badass Adorable:
- Brainwashed and Crazy: Fartor once did this to him so that he could use him for his geology skills.
- Gasshole: When he was brainwashed by Fartor, he became this.
- Genius Bruiser: Hinted to be the most intelligent Grossologist on the team, and again, he does a lot of fighting too.
- The Lancer: Abby's brother and partner in the job.
- Little Mister Badass: Also a teenager and fights very well.
- Teen Genius: Just like his sister, he very knowledgeable in science, and implied to be the smartest in the team.
- Basement-Dweller: He does nothing but sit around the lab all day, and some episodes note that he rarely ever goes outside.
- Black and Nerdy: Rivals the siblings in the science department.
- Blue Is Heroic: He wears all blue.
- Expy: He is basically an older and skinnier version of Wade from Kim Possible
- Gadgeteer Genius: He often builds contraptions for Abby and Ty to use on their missions.
- Loyal Animal Companion: Hermes, his pet rat.
- Only Known by Their Nickname: He's rarely called by his first name.
- Teen Genius: Just like Abby and Ty, he's a pretty smart guy and even builds most of the gadgets they use.
- The Smart Guy: Well, all three of the kids are intelligent, but he's the one that does all the technical work.
- Fartillery: In "Fart Side of the Moon", he out of all characters saves the day using a "powerful butt blast", due to his recent "bean-only" diet resulting in rampant flatulence.
- Neat Freak: Even the slightest hint of anything gross will send him into a panic.
- Nervous Wreck: Every time when there's a situation going on, he freaks out over the grossness of it.
- Pointy-Haired Boss: Not exactly competent at his job and can be ditzy at times.
- Running Gag: His squeamishness will be brought up Once per Episode.
- Small Name, Big Ego: Occasionally tries to take credit for Ty and Abby's successes. This never works, though.
- Amazing Technicolor Population: She has pale greenish-grey skin, although it appears pale purple in dark areas.
- Enemy Mine: Had one with Abby to fight a villain that was threatening both of them.
- Evil Old Folks: Has definitely aged a lot since her days as a university student.
- Friend to Bugs: To the point where she wants bugs to conquer the planet.
- I Was Quite the Looker: Was quite beautiful during her days as a normal scientist.
- Glasgow Grin: Appears to have this.
- Pest Controller: Obviously.
- Rapunzel Hair: She has lots of hair, and it's just about as long as Abby's.
- Red Eyes, Take Warning: Her eyes are different shades of red.
- Scary Teeth: Has sharp fangs, befitting for her creepy nature.
The Slim Slime Man
- Benevolent Boss: He treats his slime mold minions like a group of kindergartners, even telling them to pick a "surface buddy" for their invasion of the surface world.
- Blob Monster: Part-man, part-slime mold.
- Glowing Eyes of Doom: His eyes glow yellow.
- Amazing Technicolor Population: Has blue-grey skin.
- Benevolent Boss: His kind treatment of Ty even after brainwashing him into becoming his minion.
- Body Horror: He was normal human who mutated into a bloated, grey-skinned, methane-reliant monstrosity.
- Fartillery: It's all in his name.
- Gasshole: His abilities revolve around farting and he even breaths methane as a substitute for oxygen.
- Gonk: Post-mutation.
- Powered Armor: He wears this to help him breath and fly around.
- Tragic Villain: His motivations are more out of spite over his condition than out of evil.
- Used to Be a Sweet Kid: He used to be a normal kid named Larry, until his brother's constant Dutch Ovens caused him to mutate into Fartor.
- Woobie, Destroyer of Worlds: Started out as a normal kid who suffered abused by his brother, now turned into a villainous abomination.
- Amazing Technicolor Population: Sickly greenish-yellow skin. Subverted as it's actually the filth coating him.
- Ambiguously Human: He looks more gorilla-like than human.
- The Brute: His large size and strength makes him a threat.
- Evil Albino: He's actually one, and only appears green because of how much filth he has on him.
- Fat Bastard: Overweight and a nuisance to everyone around him.
- Fat Slob: He isn't called "Sloppy Joe" for nothing.
- Gonk: Not exactly in the good-looking department.
- Not-So-Harmless Villain: Most of the time he's more of an annoying petty criminal than actually dangerous, but it's shown that some of his actions can have disastrous consequences, such as in "Yack Attack".
- Obliviously Evil: Occasionally he can fall into this. In "Yack Attack", he just wanted to go for a swim in his own quiet vacation spot. The problem is that his "vacation spot" was actually the city's water supply, and he was unknowingly passing his germs to everyone and making them extremely sick.
- Pet the Dog: Turns out he has a soft spot for Christmas, and genuinely tries to be cheerful and spirited in "Let Them Eat Fruitcake", even giving Abby a present.
- The Pig Pen: Sloppy Joe is covered filth and all of his plans tend to involve filth in some way.
- Uncleanliness Is Next to Ungodliness: No surprise there, since his gimmick is that he never bathes and uses his filth as a weapon.
- Weaksauce Weakness: Clean water or just taking a bath in general. While it doesn't really hurt him, he hates it and being sparkling clean will leave him with a Villainous BSoD.
- Yellow Eyes of Sneakiness: Has yellow eyes, and is a criminal.
The Scab Fairy
- Beauty Is Never Tarnished: Her entire character revolves around averting this.
- Faux Affably Evil: She often acts like a sweet and giggling fairy, but in reality she's evil and vindictive.
- Green-Eyed Monster: Her motivation is jealousy.
- Pink Means Feminine: Her suit is pink.
- Bald of Evil: Well, your head turning into a boil can do a number on your hair.
- Beard of Evil: He has a goatee.
- Body Horror: His head is a giant zit.
- Evil Laugh: Parodied. At one point he forgot to laugh maniacally, and promptly does so.
- FaceHeel Turn: He was originally a Grossologist.
- The Grinch: He tries to ruin Christmas in "Let Them Eat Fruitcake".
- I Was Quite a Looker: Used to be tall and handsome.
- Mad Scientist: For example, creating a ray gun that causes nasty diarrhea.
- Tall, Dark, and Handsome: Was this pre-mutation.
- Your Head Asplode: His head has "popped" on a few occasions, and the results look as pleasant as they sound.
Keith "V.K." Van Kobbler
- Animal Motif: Owls.
- Butt-Monkey: Constantly has to clean the pigeon poop. This eventually lead to him getting revenge.
- Gadgeteer Genius: He has a giant owl mecha that he built himself.
- Miniature Senior Citizen: He's much shorter than the students.
- Nervous Wreck: He's terrified of Paige, and has the delusion that the pigeons are intelligent and out to get him.
- Nerd Glasses: He has round, oversized glasses.
- All of the Other Reindeer: He is bullied in school.
- Make Them Rot: His rotting powers.
- Super-Powered Evil Side: His alter-ego, Kid Rot, overpowers him.
- Villainous Crush: He has a crush on Abby as both Chester and Kid Rot, though it's far more pronounced with the latter. Abby herself seems to have a thing for Chester, but loathes his Kid Rot persona.
- Walking Wasteland: Everything he touches rots.
Dr. Cornelius Colon
- Attack Animal: Has these in the form of giant intestinal parasites.
- Mad Scientist: A typical one, all boiling down to the wardrobe, weird experiments, and Morally Ambiguous Doctorate.
- Morally Ambiguous Doctorate: He uses his knowledge in proctology to aid in his plan.
- Unfortunate Name: Resulting in his Start of Darkness.
- Blob Monster: Made entirely out of snot.
- Weaksauce Weakness: Its only weakness is dirt particles just like any mucus, which cause him to not only dry up, but decrease in size.
- Animal Motif: Bats.
- Dark Is Evil: His entire theme.
- Eerie Pale-Skinned Brunette: Has the vampire look, and is definitely eerie to boot.
- Goth: Paige referred to him as one, though he takes offense to it.
- No Celebrities Were Harmed: Based on Ozzy Osbourne.
- Amazing Technicolor Population: Green, due to her being a plant naturally.
- Beauty Mark: Has one just below her nose.
- Expy: She looks very similar to Ursula.
- Plant Person: She is part-human, part-plant.
- Animal Motif: Spiders, of course.
- I Was Quite a Looker: Like her sister, she was pretty cute as a kid.
- Pest Controller: Just like her sister, though this time she controls arachnids like spiders.
- Mad Scientist: A biochemist whose experiments cause his hair to gain superpowers.
- Prehensile Hair: He uses his hair as a weapon.
- Eye Scream: His diseased right eye.
- Balloon Belly: Turns out that Basso is obese because of all the gas built up inside him.
- Big Eater: Eats a lot of meat and other rich foods, which help fuel his burping powers.
- Evil Sounds Deep: Has a baritone voice, though it's noticeably higher when he's skinny.
- Fat Bastard: Though he's actually just bloated, rather than fat.
- Fat Slob: If his powers didn't already tip you off, his eating habits are disgusting as well, gorging nonstop on greasy foods and his shirt even being covered in grease stains.
- Karma Houdini: His episode ends with him running away, presumably getting away scott-free with his destruction and havoc.
- Jerkass: He is extremely rude to Mr. Archer even after the latter stated he was a huge fan of his.
- Gasshole: His burping abilities.
- Gonk: Probably not as much as some other villains on this show, but he's still in no way pleasant-looking, even before getting extremely big.
- Make Me Wanna Shout: His sonic belches serve as this, even being able to shatter glass.
- Ominous Opera Cape: Naturally, due to him being an opera singer.
- Ax-Crazy: In addition to evil, he's also downright insane.
- Evil Old Folks: Quit old and decrepit-looking.
- Scary Teeth: His jagged, rotten teeth give off this impression.
- Sweet Tooth: Which resulted in his rotten teeth.
- Alpha Bitch: She is quite mean to Abby and generally acts rude to everyone.
- Beauty Is Never Tarnished: Averted. Despite being the snobbish and prudish Alpha Bitch, she is still prone to gross things like farting.
- Girly Girl with a Tomboy Streak: Despite being a girly Alpha Bitch, she enjoys sports such as basketball and even challenges Abby to a chocolate shake-drinking contest in one episode.
- Girl Posse: She has two syncophants who blindly follow her around.
- Pink Means Feminine: She wears all pink.
- The Cutie: A very cute and friendly girl.
- Nice Girl
- Official Couple: Becomes this with Ty eventually.
Harvey and Petunia Archer
- Bumbling Dad: Harvey can be this at times.
- Bunny-Ears Lawyer: Despite Harvey's goofiness, he works at a water treatment center and seems to know his stuff. Same for Petunia and her job as an entomologist.
- The Ditz: Both of them are not exactly bright.
- Gasshole: Harvey becomes this in "Ain't Over 'Til The Fat Man Sings", unaware that his burping is annoying to his wife and children.
- Nerd: Harvey has this look and personality.
- Parental Obliviousness: They are completely unaware that their kids are out doing dangerous spy missions.
- Strong Family Resemblance: They both look eerily similar to their kids.
- Why Did It Have to Be Snakes?: Petunia is afraid of heights.