'''''Main Characters'''''

::'''Joel Dawson'''

Resident mad scientist of the show, Joel spends most of his time inventing insane things and making Phil's life unmanageable.

* AntiGravityClothing: In his final art design, his hat floated above his head.
* BigOlEyebrows: His final art design used these.
* BrilliantButLazy
* TheCasanova: In High Score (before Bonus Stage), Joel was presumably June's boyfriend (she's much less acknowledged in Bonus Stage), but even in Bonus Stage, Joel's the object of Elly's affection, he starts dating Jessica, and then it's later revealed he has an ex-wife.
* ChickMagnet
* CloudCuckoolander: Many of his "inventions" were pretty out there, even for being a mad scientist.
--> '''Phil''': what does it do?
--> '''Joel''': YourMom
--> '''Phil''': That's... actually pretty impressive.
--> '''Joel''': Yes. I call it the ''Up Yours''
* TheDitz
** GeniusDitz: He's a damn good inventor/scientist when he wants to be.
* TheFool
* JerkAss: While the vast majority of the cast qualifies, Joel is one of the biggest offenders.
* LongPants
* MadScientist
* {{Pirate}}: Well he said he is.

::'''Phil Argus'''

Joel's roommate and straight man.
* TheAlcoholic: More of an InformedAttribute, as his alcoholism is brought up a lot more than he's ever shown actually drinking. But it is brought up quite a bit.
* ButtMonkey
* DoggedNiceGuy: If he's trying to be nice to someone, expect it to backfire.
* InformedDeformity: Phil is treated as horrifically ugly, especially by women, despite not looking appreciably different from any other character. As with many character traits in the show, this is increasingly forgotten later on.
* JerkAss: Moreso to Joel than anyone else.
* RoundBushyHair
* ShipperOnDeck: Made a FanFiction shipping himself and Elly.
* StraightMan: To Joel.


::'''Elly Strife'''

Joel and Phil's neighbor, and the target of Phil's affection, but she only has eyes for Joel.
* EyeGlasses
* OrangeBlueContrast: Wore an orange undershirt under a blue shirt (before it switched to white).
* StalkerWithACrush: Starts off as one to Joel but mellows out as the series goes on.
-->(From one of Phil's flashbacks) "I love Joel even though he doesn't love me."
* TheOtherDarrin: Swithces voices three quaters of the way through the series. Lampshaded as her apparently having a frong in her throat the whole time.
* [[YouGottaHaveBlueHair You Gotta Have Green Hair]]

::'''Rya Botkins'''

A DeadpanSnarker RobotGirl, built by Joel to be Phil's girlfriend.

* DeadpanSnarker: Even moreso than the rest of the cast.
* DeceptivelyHumanRobots: Not to most of the cast, but apparently Craig didn't realize she was a robot, even ''after their (clearly robotic) son was born''.
* FieryRedhead
* JerkAss: Hates pretty much everyone, and it shows. Later in the series, she arguably delves into JerkassWoobie territory, what with her desire to [[spoiler: become human]] and all.
* [[spoiler:KilledOffForReal]]
* PinocchioSyndrome: [[spoiler: Eventually fulfilled, but she dies soon after.]]
* RoaringRampageOfRevenge: Had one after she and Craig broke up.
* RoboticPsychopath: Hates most of the cast.
* {{Sexbot}}: Played with. While she was built to be Phil's girlfriend, and is capable of sex (and, for whatever reason, pregnancy), Craig learned the hard way that sex with Rya can be downright dangerous.
* SyntheticVoiceActor: Was voiced by a Macintosh text-to-speech synthesizer for her earlier appearances. Later went on to being a ComputerVoice.
* {{Tsundere}}: Type A, to Phil, as a result of Joel trying to hard to make her "hard to get".


::'''Jessica Argus'''

Phil's de-aged mother.

* AbsurdlyYouthfulMother: Looks and acts 25 years old, due to Joel's experimentation in de-aging.
* ChristmasCake: In a sense. Jessica is chronologically middle-aged, but is physically and mentally in her mid-20s; however, it's implied that Joel was attracted to her even before she was de-aged.
* CloudCuckooLander: By the time the team lands on Hydrox, she's more of one than Joel.
* GranolaGirl
* TheFundamentalist: Prior to her exposure to the Sitcom Reactor, Jessica was an extremely overzealous Catholic.

::'''Cassidy'''

A former classmate of Joel, Phil, and Elly. Was known as Hat Boy in grade school.

* [[spoiler:LoveMakesYouEvil: According to WordOfGod, Cassidy was the cloaked figure from episode 79--her motivation behind killing Rya (and, had the series continued, attempting to kill Elly) was that she viewed the other girls as threats to her potential relationship with Phil.]]
* [[spoiler:MurderTheHypotenuse]]
* NiceHat: Which was apparently her defining feature as far back as ''grade school''.
* OnlyOneName: While all the other major characters have at least had their surnames alluded to in some way (such as Rya's being shown as Botkins in the credits to one episode, and June's being shown as Crane in High Score), Cassidy's is never mentioned, not even as a joke.
* SheIsAllGrownUp
* [[spoiler:StalkerWithACrush]]
* [[spoiler:Yandere: An arguable example. She initially seems sweet and level-headed, but her apparent StalkerWithACrush feelings towards Phil and the fact that she killed Rya as a result could definitely place her under the Yandere heading.]]
* YouGottaHaveBlueHair: Gradient black/blue, possibly intended to be viewed as black with blue streaks.

::'''June Crane'''

A former (and possibly current) girlfriend of Joel's. May or may not be a robot.

* AmbiguouslyHuman/AmbiguousRobots
* BareYourMidriff
* DetachedSleeves
* TheScrappy: In universe, everyone seems to go out of their way to not acknowledge her.
* [[YouGottaHaveBlueHair You Gotta Have Pink Hair]]