|First Appearance||Ken 10|
Maxatomars are a species from an unknown planet.
Maxatomars are orange, scaly and bloated with large orange and pink noses, pointed ears and bad teeth. Only male Maxatomars have been seen, so it's unknown what female Maxatomars look like.
- Billy Alien
- Billy Alien's father
- The name Maxatomar is based on Maxwell Atoms, the main creator of The Grim Adventures of Billy and Mandy. The appearance is based on Billy (voiced by Richard Horvitz), one of the show's main characters.
- As revealed in the enhanced pop-up episode, Ken 10, Maxatomars are thought to be the funniest aliens in the universe.