Marco is a famous talcum powder model, so famous he doesn't need a surname to be known! He appears in "Just Add Water".
In a chance encounter at the beauty salon Tres Tress (where he was immediately surrounded by staff hoping for reflected glory), Quinn was able to get Marco to go on a date with her to the school Casino Night - he was won over by her shallow blather about the less fortunate not having proper grooming assistance (the staff were not happy), and considered her thoughtful. "You know, I used to go out with my hair uncombed and stuff, but then I realized that by looking good, I'm bringing a little beauty into the lives of people surrounded by their own ugliness."
Quinn told everyone at school about Marco and was left distraught when he stood her up, with Sandi putting the boot in until she got stood up. As it turned out, Marco had just shown up a bit late and was wondering where everyone was (and was soon latched onto by DeeDee).
In "Love is a Way Too Many Splendored Thing", Quinn lamented: "Stay away from talcum powder models. It's not worth the heartache!"