Marcus is the "technician" of the ship, despite not even remotely knowing what he's doing. He tends to just go around hitting things with a wrench and hoping for the best. He's a stereotypical bored teenager, putting minimal effort into what he does. That being said, he does take himself seriously, and also cares about the other crewmates, particularly his sister. Marcus and his sister are the only humans on board. Despite being "supporting", he is a major character.

As mentioned above, Marcus should sound like a groggy, bored, tired, emo-esque teenager.

Think Zuko from avatar, but lower pitched.