First Appearance: #1
Casey is a perfect example of a mad scientist bent on global domination. One way or another, all of his inventions have something to do with that goal. He frequently slips into his "Dr. X" persona, wherein he dons a black mask and talks like an evil overlord. He has the technical genius to accomplish his goals, but he is often distracted or unintentionally thwarted by Andy's poorly thought out actions. Also, he seems to be a target for abuse by aliens. His girlfriend, Mary, loves him nonetheless. If there is a leader to the strange assortment of people living in the house, it is Casey.
- Mad Scientist: Andy may make equally destructive inventions, but Casey (mostly as "Dr. X") is more likely to use them for personal gain.
- The Wonka: Casey, contrasting and complementing Cloudcuckoolander Andy.
First Appearance: #1
Andy is a lunatic. The things he does don't always make sense, even in his own deranged mind. His girlfriend is Satan. He has died innumerable times. He dabbles with dark magic and mad science. His best friend and worst enemy is Casey. He doesn't get along too well with Casey's girlfriend, Mary, and the feeling is mutual. But, while disliking her, he has never actually tried to kill her (except for the punji trap), unlike with Casey. He has repeatedly killed not just Casey, but himself as well, usually by mistake.
- Artificial Limbs: In the final story arc, his right arm is ripped off, and he replaces it with an Arm-O-Mat.
- Author Avatar: The main cast is based on people in the real Andy Weir's life.
- Cloudcuckoolander: Andy. Casey, by contrast, is more of a Wonka.
- Manchild: Andy is the endearing kind; he never loses his childlike enthusiasm and wonder.
- Perverse Sexual Lust: Towards Frances Cleveland. Who turns out to be a former form of his current girlfriend, Satan.
First Appearance: #10
Mary is Casey's girlfriend. She must really love him to put up with his quirks (trying to take over the world) and his roommate. She is by far the easiest to get along with in the household. She is a normal woman trapped in a paranormal household containing two mad scientists and the Dark Lord of Evil. Still, she seems to take everything in stride, and only feels called upon to set Andy on fire from time to time. Despite hating Andy, she gets along with his girlfriend, Satan, quite well, and the two often have tea and "girl talk".
- Geeky Turn-On: One strip has Casey admit it's hot that, despite Mary's otherwise lack of extreme nerdiness, she knows some obscure Lord of the Rings trivia.
- Sitcom Arch-Nemesis: To Andy, made worse by the fact that they live in the same house.
First Appearance: #12
Satan is the fallen angel, cast out of paradise by the LORD. She can assume any shape, and she has chosen this one for now. She is the celestial embodiment of evil, and Andy's girlfriend. Despite her job and reputation, she is easy enough to get along with, and actually quite polite. For the most part, she only uses her immense evil powers in small ways, but there's always the hint that she could do more if she wanted to.
- Ascended Demon: Satan briefly returns to her status as an archangel during Azriel's attempted takeover of Hell (which serves as an example of Shown Their Work — according to Christian theology, Lucifer was an archangel before being cast out of Heaven).
- Horny Devils: Lampshaded
- Ms. Fanservice: Satan
- Not a Morning Person: In one strip, Satan is literally a monster until she gets her cup of coffee.
- Satan is Good: Or at very least, really adorable.
- Story-Breaker Power: Obviously. Every ongoing story arc needed some reason she couldn't or wouldn't solve the problem with a quick handwave, such as enjoying being tied up when captured, or her past incarnation being the villain.
- Too Kinky to Torture: Our heroes have been tied up by the bad guy. Satan obviously could break free from her bonds and free them—but she really likes being tied up.
First Appearance: #39
An incredibly smart, talented, and noble officer of the law.
- The Ace: Quantum Cop starts out knowing everything except bovine dentistry. A strangely high number of his solutions to quantum mechanics problems involve hitting people with sticks.
- Can Not Tell A Lie: Quantum Cop can't lie. He eventually gains the ability in the final arc as Character Development.
- The Stoic: Most of the time.
First Appearance: #117
First Appearance: #8
Andy's pet cat.
The Planet Devourer
First Appearance: #312
One of Dr. X's failed experiments to dominate the world. Is capable of devouring anything...eventually.
First Appearance: #311
Jenn's time-travelling daughter, who only appears when her future existence is threatened.
First Appearance: #90
An Evil Overlord
whose base is in Japan. Considers himself Casey and Andy's arch-enemy, though the true reason why (as well as his origin) isn't revealed until the final story arc.
The Mime Assassin
First Appearance: #90
First Appearance: #138
Satan's #2, who tries to usurp her when her love for Andy has made her vulnerable.
- Oh, Crap!: Azrael tries to supplant her by absorbing all her evil, thinking it will make her disappear. Instead, he turns her into the Archangel Lucifer, who proceeds to kick his ass.
First Appearance: #153
First Appearance: #197
First Appearance: #200
First Appearance: #223
First Appearance: #447
First Appearance: #450
First Appearance: #452
- Bait-and-Switch: Jenn assumes she's an assassin when they meet, and that she's about to be saved by a Quantum Paladin, which turns out to be a Stygian Zealot after her life.
- Distaff Counterpart: To Quantum Cop.
The Stygian Zealot
First Appearance: #453
First Appearance: #455
First Appearance: #2
The Grim Reaper
. Often collects Casey and Andy's souls after an invention goes wrong, though he backs off more often after his boss Satan gets involved.
The Religious Zealot
First Appearance: #25
A door-to-door evangelist that frequently tries to convert Casey and Andy. Ironically, he gets along well with Satan.
- I Choose to Stay: In the final arc, the LORD convinces him to stay in 1887, since everyone is just as concerned about morality and evangelism as the Zealot.
First Appearance: #127
The head of the local homeowner's association. Occasionally harasses Jenn, but outright avoids her neighbors.
Wellhung of the Hunkinites
First Appearance: #159
The ambassador of an attractive, muscular alien race that make Jenn their queen. However, it is mostly just a title, as she's "rescued" before she can go with them.
The Bug Fairy
First Appearance: #167
A small fairy that specializes in programming bugs...causing
them, that is, rather than debugging.
King Carl XVI Gustav of Sweden
First Appearance: #419
The King of Sweden. After personally delivering a peace prize to Quantum Cop, he decides to spend the rest of his days on Casey and Andy's couch instead of returning to his kingdom.
- Generation Xerox: In the epilogue, his daughter takes both the crown of Sweden and the spot on Casey's couch after Carl's eventual death.
- The Thing That Would Not Leave: Despite all attempts, he refuses to return to Sweden, to the point that Sweden's citizens actually send him back to his "rightful place" on the couch after he's sent home.
First Appearance: #515
Andy's most hated president. Thanks to fortunetelling, the feeling is mutual.
First Appearance: #598
First Appearance: #517
Bob was there, too.
- The Omnipresent: Bob has the ability to "be there, too". Meaning that any sentence can be affixed with "Bob was there, too." In essence Bob is (or at least, can be) everywhere.