Chuny Marquez has been a nurse at County since the beginning. She is first seen as a nurse on the maternity ward in Season 1, but transfers to the ER by the start of Season 2. She is a regular presence for the rest of the show's run. She is featured on the show as a character of greater import in ebbs and flows. She notably helps Dr. Mark Greene get over his divorce, breaking up with him before he can leave her.
She is known for her reliability, knowledge, and dry humor. Her first language is Spanish, and she is often called upon to act as a Spanish-English interpreter.