- Joel Dawson
Resident mad scientist of the show, Joel spends most of his time inventing insane things and making Phil's life unmanageable.
- Phil Argus
Joel's roommate and straight man.
- Elly Strife
Joel and Phil's neighbor, and the target of Phil's affection, but she only has eyes for Joel.
- Rya Botkins
A Deadpan Snarker Robot Girl
, built by Joel to be Phil's girlfriend.
- Deadpan Snarker: Even moreso than the rest of the cast.
- Deceptively Human Robots: Not to most of the cast, but apparently Craig didn't realize she was a robot, even after their (clearly robotic) son was born.
- Fiery Redhead
- Jerk Ass: Hates pretty much everyone, and it shows. Later in the series, she arguably delves into Jerkass Woobie territory, what with her desire to become human and all.
- Killed Off for Real
- Pinocchio Syndrome: Eventually fulfilled, but she dies soon after.
- Roaring Rampage of Revenge: Had one after she and Craig broke up.
- Robotic Psychopath: 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.
- Synthetic Voice Actor: Was voiced by a Macintosh text-to-speech synthesizer for her earlier appearances. Later went on to being a Computer Voice.
- 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.
- Absurdly Youthful Mother: Looks and acts 25 years old, due to Joel's experimentation in de-aging.
- Christmas Cake: 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.
- Cloud Cuckoo Lander: By the time the team lands on Hydrox, she's more of one than Joel.
- Granola Girl
- The Fundamentalist: Prior to her exposure to the Sitcom Reactor, Jessica was an extremely overzealous Catholic.
A former classmate of Joel, Phil, and Elly. Was known as Hat Boy in grade school.
A former (and possibly current) girlfriend of Joel's. May or may not be a robot.