Mark is a fictional character played by Jeffrey Muller in the television series The Office. He was Jim's room mate until Jim moved out and bought his parent's old house to have a home for him and Pam.
Season 2:
Mark is Jim's roommate who was very interested in meeting Jim's co-workers based on the stories he has heard. He was especially interested in meeting Dwight because he didn't believe that Dwight could be real. Mark was very impressed when he met Dwight and realized that Jim was telling the truth. He has a girlfriend but her name is not mentioned.