Keith Dudemeister is a medical resident at Sacred Heart. Originally, Keith was introduced as a timid intern, and found it very difficult to muster the courage to talk. After a period of sucking up to J.D. he eventually became very popular and adapted quickly to his hospital responsibilities. After he started coming along, J.D. grew to dislike Keith. When Keith began dating Elliot, J.D. found himself caught in the middle. However, J.D. soon saved them both when their jobs were in jeopardy and decided that he would get along with Keith for Elliot's sake. He admitted that Keith had genuine skills as a doctor, and the two of them got along well until Elliot broke off her engagement.

Keith reveals himself to be a Republican("His Story IV"), which strengthens the relationship between him and Elliot, as she is also one. Keith has a sister namedDenise who Elliot once said was very attractive. He also has an uncle named Ronald and an aunt named Alicia. His uncle Ronald "doinked" Elliot's mother.