Marco Diaz

Marco Díaz is the deuteragonist of Star vs. the Forces of Evil. A Hispanic California citizen, he has been assigned the task of helping Star Butterfly adjust to Earth, and of providing Star with a home thereon. He has also come to serve the additional roles of aiding Star in fighting all matter of inter-dimensional monsters, and apparently has even begun to form a friendship of sorts with her. He is voiced by Adam McArthur.

Personality
Marco is practically the exact opposite of Star. He is very wary and tries to avoid any trouble or exposure. Because of Marco's cautiousness (and the one time he wore a helmet in the gym shower), he is labeled by both his peers and school staff as the "safe kid." Ironically, despite his predilection toward practical caution, Marco seems to enjoy the prospect of combat and adventure (In the pilot episode, he even expressed a desire for "some action and danger in (his) life"). Marco also seems to want this to be opined so with his reputation, as well; Marco openly expresses disdain for being considered a "Safe Kid", and has repeatedly attempted (to little avail) to persuade others to view him as otherwise.

Marco has proven to be notably irritable, as seen in his rambling about his reputation in the pilot episode, and his very quickly losing patience with Star in the same episode. He has also demonstrated poor sportsmanship, elevating himself and slandering his opponents in the Arcade Dimension of the episode immediately following, though this may have simply been on account of his anger and defensiveness against Pony Head, due to her mistreatment and threats against him.

Marco seems to have studied martial arts extensively, namely Karate, as seen in the pilot episode. He can also briefly be seen in the introductory animated sequence trying to build up strength to break a wooden board, a common test of strength and technique in East-Asian martial arts.

Introduction
In the Pilot episode, Marco was chosen by the school principal in the pilot episode to guide and show Star around due to his reputation. As he discovered upon returning home on the same day (after discovering Star's bizarre background), his home was also selected to be Star's own, though the person or persons who made this decision and the means by which it was reached remain as-yet unknown.

Immediately following his interactions with Star, Marco ran away from home, abhorrent of his new roommate. Star managed to find him afterwards, and acknowledged the hardship she had put him through. Prior to closure being fully reached, the two were ambushed by the villain Ludo and his thugs. Fighting Ludo and his thugs with Star, Marco expressed a change of heart toward Star, having shed his previous ire. The two immediately returned to his home following this reconciliation.