Marcus was a truck driver for Red's Roofies, who picked up Ms. Crabtree when she went to get help for the stranded school bus in "City on the Edge of Forever (Flashbacks)". He was attracted to Ms. Crabtree. He attempted to give her "roofies", however, they had no effect on her. Aiming to assist her in finding help for the kids, Marcus instead wound up getting caught up in her newfound fame as a comedian, and accompanied Crabtree first to Denver and then to The Tonight Show. Afterwards, the two fell in love, although Marcus warned Mrs. Crabtree that he could not "stay" due to the events all being a third grader's dream.
He has short, black hair. He wears a blue "dress" shirt, dark gray pants, and a gray-buckled, black belt.
He seems to be willing to "date rape" a woman, as he gave Mrs. Crabtree "roofies", a common "date rape" drug. Later in the episode, he seemed to be kind, later falling in love with Mrs. Crabtree and treating her with the utmost respect. He is possibly an allusion to Elvis Presley.