Child Hater: Has a rather comical rivalry with the local kids. Downplayed but somewhat justified as they often pick on him specifically and seem to have somehow acquired military training and weapons, such as tear gas.
Cool Bike: The squirrels improved his moped, so he could get safely to work on the frozen roads. They gave it multible legs making it similar to a large legged Robot. Naturally, Art is very thankful for it.
Death Glare: Arthur's on the receiving end of one from both Kat and Hilary (mostly from Kat), justified since he jokingly suggested them to work together to make money and was a bit perverted.
Art talked Pip out of beginning a relationsship with Fern whom the penguin had met in an online game. His reasons were justified though, since the odds weren't in Pip's favor that Fern actually was as attractive as her in-game avatar and was more likely to be someone like Pip himself, a guy as well. Art was wrong.
He doesn't support Pip's relationship with Hilary either, which is justified. Initially, he was supportive of it, but then Hilary broke Pip's heart.
Team Dad: Downplayed and mixed with Cloudcuckoolander's Minder, Art acts like a father figure as he’s in charge of telling the Squirrelgirls about morals, not eating everything in the house and what the denizens can do (specifically keeping their creepy butts in the basement). When he discovered that the Squirrels had kept King Liam cleaning up the basement for years, Art was relieved since "How deceiving someone into permanent servitude is wrong", is a much easier subject as opposed to telling them about relationships.
Fan Girl: While normally very collected, Kat cannot keep her inner fangirl under control on subjects like computer games, movies, anime and film stars, and gladly buying merchandise, perhaps even going a tad crazy in the process.
In the Q&A strips, she was asked what her favorite type of yarn was. She responded that she liked cotton best as it's hard-wearing and less likely to break when bitten, and that she "needs some alone time" while blushing furiously. Zig-zagged as she doesn't follow a laserpointer around.
A Date with Rosie Palms: Much to his roommates' chagrin, he frequently does this, and leaves his porn collection to be found after wards. He once commented that a terabyte of porn would only get him through a week.
Amicable Exes: Even after all Hilary did, Pip is still willing to sell things to her on a regular basis, he justifies it, claiming she's "a good customer".
It's to the point he has police level riot gear, just in case there's ever a zombie outbreak (it crosses into the field of Crazy-Prepared since he has gear in Art's size). Pip usually uses it for when there is a comic-convention.
Comedic Sociopath: Often cowardly while at home, but he sticks up for his friends during the battles in later arcs.
Cosplay: Pip have a passion for this and have no reservations about who he cosplays (like Catwoman).
Dirty Coward: When the pair was confronted by Jack, Pip fled instantly, leaving Scarlet to fend for herself and locked the door behind him.
Furry Reminder: Pip has one of these when Kat is chastising him for not wanting to feed Leonard. He points out that his natural paternal instincts do make him want to feed Leonard, but he's fighting it because birds feed their young by regurgitating food into their mouths. Pip has another reminder when it comes up that he has to "double flush" when he poops because "birds can't chew".
Geek: Big time! Be it video games (especially Lorecraft), movies or comics, Pip is into it on an almost religious level. He considers his comic collection to be so vast, that it can act as a counterweight to a destabilized building!
Greed: Pip has been called an "arch-capitalist" and he repeatedly proves that the title is rightfully earned. There's nothing that penguin won't sell online, case in point: One of the first things he tried to do with Scarlet was to sell her to a guy named Eurin. The only reason the sale went through was because Kat got involved. This trait sometimes leads into Unwitting Instigator of Doom territory, such as when he sold an ensorcelled closet or a button that allegedly kills people when pushed (the latter for free).
Hidden Depths: During his time with Hilary he revealed in his sleep that he was legitimately happy to be dating her not just because of her looks, but because Hilary seemingly shared his interests and wanted to spend time with him. The very same comic where he admits this also had him drugged and saying it in his sleep while Hilary went off to have sex with her actual boyfriend.
Jerkass: Definitely the rudest out of the main characters.
Unsympathetic Comedy Protagonist: When bad things to happen to him, it's usually the result of karma for him being an asshole. Except for what Hilary did to him.
"Ok, something happened, but I'm mostly positive it wasn't bad"
Accidental Pervert: Together with her sisters, they design of the Candycane 2.0, completely oblivious to its heavy resemblance to something else. It takes Kat whispering in her ear to explain why their distribution attempts to a child got them arrested.
Big Eater: Scarlett have repeatedly been shown to eat absurd amounts of food, such as her own weight in Christmas confectionary or everything in the fridge, which is normal for her. She never gains an extra pound for it though, as lampshaded by Kat below.
Kat: "Where the hell do you put all that stuff, anyway?"
Did Not Think This Through: Her inability to focus sometimes channels into her not considering the long term ramifications of her actions, like how the inventions and modifications she creates may backfire.
Dreadful Musician: As Kat and Art have learned to their chagrin. Once Pip even sent her to sing to Kat as a prank, while she was hungover.
Gadgeteer Genius: Even without her sisters, she's capable of devising spectacular gadgets.
Genius Ditz: She's the trope picture for a reason - she can make impossible sci-fi devices, but has some significant problems with basic common-sense and self-preservation instincts. She hates candy canes due to their shape from eating one by the straight end and hitting her own eye with the curve, and she along with her sisters created a perpetual motion machine from a slinky (until it explodes, apparently) because they thought it was sad it couldn't go up stairs.
Hive Mind: With her sisters. Their connection is the reason why Scarlet is such a ditz early on.
Innocent Fanservice Girl: Though she's not so innocent that she doesn't appreciate a gender flipped version of this trope.
The Leader: Despite sharing a hive mind with her sisters, Scarlet sometimes has to direct the other three due to being more aware of the outside world, her time away from them helping her become an individual, and because she's not agoraphobic.
Genius Ditz: They suffer this, along with Scarlet, due to being networked together and optimized to spread any intellectual load across a unified whole. When separated they not only lose most of their incredible intelligence, retaining only small segments independently, but due to their minds having worked as a single unit for so long any one of them on their own ends up with a minimal attention span and downright oblivious.
Hikikomori: Due to OZBASIC making them agoraphobic.
Hive Mind: When in proximity to each other, and Scarlet, their intellect is significantly increased to the point of genius. When together they are capable of making technological leaps as well as understanding binary code and running complex algorithms in their minds.
Basement-Dweller: Initially enforced in the literary sense as the other residents in the house finds them both creepy and disturbing. They don’t seem to care much for it and continually walk around upstairs anyway. Then again, the basement is ridiculously huge so they have plenty of space to themselves, meaning they rarely bother with the groundfloor or the attic.
Art: (to the denizens after giving them a TV) "And keep your creepy little butts in the basement."
Dark Is Not Evil: Really quite harmless without Jack around to give them orders.
The Engineer: They might be a bunch of oddballs, but they also fill several slots in this trope, they’ve even built a functional fleet of TIE-Fighters! Just because they watched a marathon!
Fanboy: They love their soap operas and Star Wars (especially Stormtroopers).
Heel–Face Turn: Like ants, they have to have a master. Kat and Art don't want to be that master (and they really don't want Pip or Scarlet to be that master).
Miming the Cues: The Denizens try to mime what a multilimbed headless horror is to Kat. It fails spectacularly.
Kat: (to the denizens) Um, ears, wrestling, rolling around… Sumo Rabbit Orgy?
Super Toughness: Downplayed, those little guys are surprisingly durable. Kat and Art tried several things to get them to leave, all in vain: vacuuming doesn’t work, emptying a can of bug spray only get three of them stoned and the denizens microwave themselves for fun.
Too Spicy For Yogsothoth: Downplayed, one denizen got caught and eaten by a bird of prey, which almost immediately vomited it back up.
The Voiceless: An impediment which they don’t seem to be aware of themselves, as one denizen tried to phone home after getting lost only for Art, who took the call, to not be able to hear anything.
Alpha Bitch: She was this in school with Kat and continues to act like one as an adult.
Attention Whore: Pretty much her motivation for 99% of everything she does. In fact, the reason she hates Kat is because they both had the same Pink Pony lunch box as little girls, and Hilary was afraid that Kat would take attention and popularity away from her because of it.
Bait-and-Switch Boss: Initially it looks like she took over Narni-Narni-Nar-Nar after Pip sold her the wardrobe with the portal. Turns out it was actually Ms. B.
Because You Were Nice to Me: During her Literal Split Personality episode, her guilty side reveals to Pip that she chose to live with him instead of just going to a hotel because she was genuinely touched that he would bother to take her back after what she did to him. It's her pride while whole that keeps her from admitting it.
Bitch in Sheep's Clothing: Pretends to be all affectionate to Pip during their time together, but in reality has been two-timing him with her actual boyfriend while using him to cover her position at the thrift store.
Brains and Bondage: Downplayed, Hilary isn't implied to be overtly educated, but she has the brains to manipulate others to rise in the hierarchy. Her sex-life with Pip is full of bondage, such as using him as a footstool, hanging him up with a gag in his mouth or using a riding crop on him.
Hate Sink: Every appearance she made showed her doing nothing but antagonizing Kat, and then later Art just because he's friends with Kat. It seemed that losing her job and all her equally slimy friends abandoning her was the karmic wake-up call she needed to be a better person, but then it turned out she was just as horrible as ever. She tricked Pip into thinking they were in a relationship by sleeping with him once, then used him to cover her shifts at the thrift store so she could sleep her way back to a high paying job. Oh, to be especially cruel, she gave Kat her store keys so she could bring them to Pip and let her be the one to tell Pip the truth just to make Kat uncomfortable.
Hidden Depths: It's so hidden that it only came out because she became a Literal Split Personality, but one separate part of Hilary highly upset with herself for her awful wrongdoings and has been suppressing her guilt the entire time to the extent that the part representing this side of her is a horribly emaciated husk of a person.
It's All About Me: She hates Kat because Kat had the exact same lunchbox when they were kids and Hilary couldn't stand the idea the lunchbox didn't make her special.
Kissing Cousins: That's what she told Pip anyway. Naturally, Kat is squicked out.
Literal Split Personality: After Kat split her from the squirrelgirls, Hilary was divided into a number of clones, which possess different aspects of the main ones' personality. One is slutty (immediately offering to show her breasts for money) while another is vengeful (threatens bodily harm on the squirrels for what they’ve done). A third clone is apologetic and readily apologizes for everything she's ever done to anyone (Kat in particular) and tearfully admits to having been a bitch. Then after those three are merged into one, Hilary's happiness is represented as a tiny fragment of her persona barely as big as the Denizens.
Manipulative Bitch: Puts on a sob story act to make Pip feel bad for her, cemented with sleeping with him, to get him to cover her hours at the thrift store. She also drugs him and makes him believe they're still having sex while it allows her to bring her actual boyfriend over and sleep with him while Pip's mumbling about how happy he is to be with Hilary.
Pyromaniac: One of her clones has this in spades, threatening others with burning down their house.
Sadist: She takes sick enjoyment in making Kat be the one to tell Pip the truth about their "Relationship". When Pip takes her back in after her house burns down, it's evolved into a semi-consensual BDSM kind of relationship.
Teacher's Pet: Miss Strinpit favored her over Kat, giving Hilary rather simple questions and then following up by forcing Kat to answer ones so complicated and overly advanced they flustered the poor girl (to which Strinpit would then give her detention for "Not listening.")
All Men Are Perverts: He represents the author, who drew himself as a hamster as it allows him to neatly fit in between Helga's cleavage.
Evil Is Petty: Many of the nasty things she does is driven by her petty desire to wear specific fashion. When first seen, she brings forth an Endless Winter to Narni-Narni-Nar-Nar just so that she can be Pretty in Mink. In her second appearance, she repays Hilary's fashion advices by turning the latter into her dragon steed. Then when Liam restores the realm to normal, she is furious because the scorched wasteland complimented her new outfit.
The Dreaded: To Art and Pip. Justified as she found where they lived and hammered at their door until the police took her away. Years later, Art can still hear the sounds he made at night.
Mask of Sanity: That she was overly attached to (and in a relationship with) a dressmaker dummy is one thing, but after Art and Pip stole the thing her mask starts falling off. By the time she figures out what they did, she goes completely off the deep end and had to be put in a mental hospital for months. The mere sight of Art several years later puts her right back in crazy mode. Even if stealing the dummy was a dick thing to do, Vanessa's response to the whole thing showed she was liable to snap at any moment.