Marcus is the camp customer assistant at Perseus. He often compliments Niko Bellic if he is wearing clothes from Perseus, and will insult him if he's wearing clothing from elsewhere. He also claims to have a nipple ring, which is mentioned in GTA IV if the player bumps into him.
Although Marcus can only be found at Perseus, pedestrian models that share the same design cues and voice actor can be spotted in Varsity Heights, The Meat Quarter and Middle Park West, occasionally dressed in a more informal sleeveless top and usually speaking in a less formal tone. Humorously, when carjacking them, Niko will use his female quotes as if they were women.