Mars the Great

Mars the Great is the secondary antagonist in the Cartoon Network's 2020 film, Adventure Time: The Hero of Ooo. He works at the Odysseus System, a crime organization owned by her boss, the infamous supervillain, Paris the Untamed.

Biography
Mars was first seen introduced Paris the Untamed. Later in the film, Mars informed Paris that there is a conference call with the United Nations waiting for him, a call in which Paris reveals that he and his forces (including Mars and the other Finn and Jake's old enemies) are threatening the Candy Kingdom with their doomsday device as part of Paris' true plan to conquer the Land of Ooo.

Finn (now an adult) moves to Burbank after learning of a new career (from Paris' henchman, Mars) that will offer healthcare benefit for himself and his family. After discussing this further with the family, an now-elderly Jake agrees to the moving, adding that they might need Jake's new salary and that their world is tearing itself apart due to the show ending and Finn's memory loss. As Finn and Jake arrive to their new house in the local headuarters of Cartoon Network, Burbank, Mars welcomes them with a gift basket before giving Jake a job as the new supervisor of employees working in the headquarters' nuclear division. In spite of Jake's incompetence as a safety inspector back in the television, Finn actually does a good job motivating Paris' employees in Cartoon Network's nuclear division (even going so far by offering them hammocks to calm them down from overworking). Because of his success, Mars happily informs that the productivity in the nuclear division is currently up 2% thanks to Jake's motivation skills, leaving his family to be very proud of him.

Despite enjoying his new job working in the real world, Finn and Jake are upset to hear that the Cartoon Network characters are very miserable living in the real world and want to return to the television (as Nicole mopes to herself since the house is capable of cleaning itself, Panda is allergic to all chicken feathers around the market, and Clarence is forced to take a remedial class due to his lack of cursive writing). Following the attempted execution of Marceline (thanks to Jake managing to foil the vampire's escape by wrestling him down), the Banana Guards have invaded the Candy Kingdom with the intention of stopping Paris. Wearing a bikini and high heels, Mars aids Paris and his men in fighting the military, using his gun to easily shot an army soldier's neck.

It is presumed that Mars is arrested along with Paris' forces for his crimes, though it would've appeared that he has managed to help Paris and his forces accomplish their goal in destroy the Candy Kingdom, as a television report detailed Paris' arrest while the heroes returned back to the television (thanks to Mars' advice to Jake on doing what's best for his family).