Who is Harold Marcus from The Pat Hobby Stories and what is their importance?

Harold Marcus appears in Pat Hobby and Orson Welles, The Homes of the Stars, and On the T. He is the head of the studio. When we first meet him, Marcus is sitting in a car gaining access to the studio. Pat begs him for a ride the studio grounds, as well as a pass to get him through security. Mr. Marcus never comes through with the pass, but Pat manages to find another way onto the studio grounds. Pat later finds himself acting as a tour guide to the houses of the stars in Hollywood.