Earth

Elliott

Voiced by: Samuel Faraci

An eleven-year-old boy and titular character of the series.

All-Loving Hero: Elliott is unwaveringly kind and friendly, even to his enemies.
Blue Is Heroic: His main outfit he's seen wearing is a blue sweater with Saturn on it.
Cheated Angle: His bangs always face the direction furthest from the camera.
Fish out of Water: Has some difficulty adjusting to the alien technology and culture of The Centrium, although thanks to his nomadic background he's able to adapt fairly quickly.
I Just Want to Have Friends: Due to his mother's job, Elliott was unable to form any long-lasting friendships with children his age.
Kiddie Kid: Downplayed and Justified, while Elliott is eleven, he has the naivety and social skills of a much younger child due to having very limited social interaction prior to arriving on the Centrium. That said, he often says surprisingly mature things or proves himself more perceptive than those around him.
Missing Mom: Not Frankie, but his second mother hasn't shown.
Nice Guy: While he does have a mischievous streak at times, Elliott is overall one of CN'S kindest heroes. Any time he says or does something rude or offensive tends to be Innocently Insensitive at worst.
Only-Child Syndrome: The lone son of Frankie which plays into his nomadic and Friendless Background.

Frankie

Voiced by: Naomi McDonald

A geologist and mother to Elliott. She aspires to uncover new geological discoveries by researching geology from space.

The Glasses Gotta Go: She starts the series off in a pair of blue glasses which are later given to Mo to help him see better. They eventually get replaced by a red pair.
Good Parents: Needless to say, she takes living in space rather well, isn't terribly worried about her son going off on his own but still watches over him when needed, and her close relationship with Elliott is based on mutual teamwork and respect.
Horrible Judge of Character: In "Wednesday" (the pilot episode), she doesn't take Elliott's suggestion to follow the creepy landlord willing to give them a home because, well, he's creepy. But when a (seemingly) nice old lady invites them to her house and Frankie is okay with it, the trio almost gets turned into statues by the old lady.
Really Moves Around: Because of her profession, she and her son have to move on a regular basis.

Voiced by: Noah Kaye Bentley

A Stegosaurus Elliott and Frankie meet in a biosphere.

Artifact Name: Mo gains his name shortly after meeting Elliott and Frankie. It's inspired by "Maureen", what Elliott's mothers planned to name him if he had been born a girl.
Blind Without 'Em: Prior to trying on Frankie's glasses, his vision was terribly blurry.
Literal-Minded: So much that when Frankie advises him to "look but don't touch" stuff has him think touching stuff is fine while his eyes are shut. Much of his thought process works like this to at least some extent.
Too Dumb to Live: He tends to be very simpleminded and not always aware of danger. Somewhat downplayed considering he's still very intelligent by his species' standards and isn't always so oblivious, not to mention he's also still a quick learner who's rather good at figuring things out with time. Also somewhat justified by his background of living alone in the biosphere's wilderness.
Vague Age: It's unclear how old he is exactly, due to his mysterious background.

Aliens

Lord Kallous the Merciless

Voiced by: David Warner

A retired supervillain who serves as Elliott and Mo's teacher.

Big Bad: He's the closest thing to a main antagonist the show has and the only recurring villain, especially since most episodes have No Antagonist.
Expy: His design is clearly based on Skeletor.
Retired Monster: He's a former planet-conquering warlord and while he doesn't do much active supervillainy, he makes no attempt to hide the fact he's still evil.
Sadist Teacher: Expected given he's a retired supervillain.